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Go lang

https://go.dev/ ↗

Go is a high-level, general-purpose programming language that is statically typed and compiled. It is known for the simplicity of its syntax and the efficiency of development that it enables through the inclusion of a large standard library supplying many needs for common projects.

Update May 7, 2026 tracked by Updatify

go1.26.3 (released 2026-05-07)

go1.26.3 (released 2026-05-07) includes security fixes to the go command, the pack tool, and the html/template, net, net/http, net/http/httputil, net/mail, and syscall packages, as well as bug fixes to the go command, the go fix command, the compiler, the linker, the runtime, and the crypto/fips140, crypto/tls, go/types, and os packages. See the Go 1.26.3 milestone on our issue tracker for details.

Original source ↗

Update May 7, 2026 tracked by Updatify

go1.25.10 (released 2026-05-07)

go1.25.10 (released 2026-05-07) includes security fixes to the go command, the pack tool, and the html/template, net, net/http, net/http/httputil, net/mail, and syscall packages, as well as bug fixes to the go command, the compiler, the linker, the runtime, and the crypto/fips140, go/types, and os packages. See the Go 1.25.10 milestone on our issue tracker for details.

Original source ↗

Update Apr 7, 2026 tracked by Updatify

go1.26.2 (released 2026-04-07)

go1.26.2 (released 2026-04-07) includes security fixes to the go command, the compiler, and the archive/tar, crypto/tls, crypto/x509, html/template, and os packages, as well as bug fixes to the go command, the go fix command, the compiler, the linker, the runtime, and the net, net/http, and net/url packages. See the Go 1.26.2 milestone on our issue tracker for details.

Original source ↗

Update Feb 10, 2026 tracked by Updatify

go1.26.0 (released 2026-02-10)

Introduction to Go 1.26

The latest Go release, version 1.26, arrives in February 2026, six months after Go 1.25. Most of its changes are in the implementation of the toolchain, runtime, and libraries. As always, the release maintains the Go 1 promise of compatibility. We expect almost all Go programs to continue to compile and run as before.

Changes to the language

The built-in new function, which creates a new variable, now allows its operand to be an expression, specifying the initial value of the variable.

This feature is particularly useful when working with serialization packages such as encoding/json or protocol buffers that use a pointer to represent an optional value, as it enables an optional field to be populated in a simple expression, for example:

import "encoding/json"

type Person struct {
    Name string   `json:"name"`
    Age  *int     `json:"age"` // age if known; nil otherwise
}

func personJSON(name string, born time.Time) ([]byte, error) {
    return json.Marshal(Person{
        Name: name,
        Age:  new(yearsSince(born)),
    })
}

func yearsSince(t time.Time) int {
    return int(time.Since(t).Hours() / (365.25 * 24)) // approximately
}

The restriction that a generic type may not refer to itself in its type parameter list has been lifted. It is now possible to specify type constraints that refer to the generic type being constrained. For instance, a generic type Adder may require that it be instantiated with a type that is like itself:

type Adder[A Adder[A]] interface {
    Add(A) A
}

func algo[A Adder[A]](x, y A) A {
    return x.Add(y)
}

Previously, the self-reference to Adder on the first line was not allowed. Besides making type constraints more powerful, this change also simplifies the spec rules for type parameters ever so slightly.

Tools

Go command

The venerable go fix command has been completely revamped and is now the home of Go’s modernizers. It provides a dependable, push-button way to update Go code bases to the latest idioms and core library APIs. The initial suite of modernizers includes dozens of fixers to make use of modern features of the Go language and library, as well a source-level inliner that allows users to automate their own API migrations using //go:fix inline directives. These fixers should not change the behavior of your program, so if you encounter any issues with a fix performed by go fix, please report it.

The rewritten go fix command builds atop the exact same Go analysis framework as go vet. This means the same analyzers that provide diagnostics in go vet can be used to suggest and apply fixes in go fix. The go fix command’s historical fixers, all of which were obsolete, have been removed.

Two upcoming Go blog posts will go into more detail on modernizers, the inliner, and how to get the most out of go fix.

go mod init now defaults to a lower go version in new go.mod files. Running go mod init using a toolchain of version 1.N.X will create a go.mod file specifying the Go version go 1.(N-1).0. Pre-release versions of 1.N will create go.mod files specifying go 1.(N-2).0. For example, the Go 1.26 release candidates will create go.mod files with go 1.24.0, and Go 1.26 and its minor releases will create go.mod files with go 1.25.0. This is intended to encourage the creation of modules that are compatible with currently supported versions of Go. For additional control over the go version in new modules, go mod init can be followed up with go get go@version.

cmd/doc, and go tool doc have been deleted. go doc can be used as a replacement for go tool doc: it takes the same flags and arguments and has the same behavior.

Pprof

The pprof tool web UI, enabled with the -http flag, now defaults to the flame graph view. The previous graph view is available in the “View -> Graph” menu, or via /ui/graph.

Runtime

New garbage collector

The Green Tea garbage collector, previously available as an experiment in Go 1.25, is now enabled by default after incorporating feedback.

This garbage collector’s design improves the performance of marking and scanning small objects through better locality and CPU scalability. Benchmark results vary, but we expect somewhere between a 10–40% reduction in garbage collection overhead in real-world programs that heavily use the garbage collector. Further improvements, on the order of 10% in garbage collection overhead, are expected when running on newer amd64-based CPU platforms (Intel Ice Lake or AMD Zen 4 and newer), as the garbage collector now leverages vector instructions for scanning small objects when possible.

The new garbage collector may be disabled by setting GOEXPERIMENT=nogreenteagc at build time. This opt-out setting is expected to be removed in Go 1.27. If you disable the new garbage collector for any reason related to its performance or behavior, please file an issue.

Faster cgo calls

The baseline runtime overhead of cgo calls has been reduced by ~30%.

Heap base address randomization

On 64-bit platforms, the runtime now randomizes the heap base address at startup. This is a security enhancement that makes it harder for attackers to predict memory addresses and exploit vulnerabilities when using cgo. This feature may be disabled by setting GOEXPERIMENT=norandomizedheapbase64 at build time. This opt-out setting is expected to be removed in a future Go release.

Experimental goroutine leak profile

A new profile type that reports leaked goroutines is now available as an experiment. The new profile type, named goroutineleak in the runtime/pprof package, may be enabled by setting GOEXPERIMENT=goroutineleakprofile at build time. Enabling the experiment also makes the profile available as a net/http/pprof endpoint, /debug/pprof/goroutineleak.

A leaked goroutine is a goroutine blocked on some concurrency primitive (channels, sync.Mutex, sync.Cond, etc) that cannot possibly become unblocked. The runtime detects leaked goroutines using the garbage collector: if a goroutine G is blocked on concurrency primitive P, and P is unreachable from any runnable goroutine or any goroutine that those could unblock, then P cannot be unblocked, so goroutine G can never wake up. While it is impossible to detect permanently blocked goroutines in all cases, this approach detects a large class of such leaks.

The following example showcases a real-world goroutine leak that can be revealed by the new profile:

type result struct {
    res workResult
    err error
}

func processWorkItems(ws []workItem) ([]workResult, error) {
    // Process work items in parallel, aggregating results in ch.
    ch := make(chan result)
    for _, w := range ws {
        go func() {
            res, err := processWorkItem(w)
            ch <- result{res, err}
        }()
    }

    // Collect the results from ch, or return an error if one is found.
    var results []workResult
    for range len(ws) {
        r := <-ch
        if r.err != nil {
            // This early return may cause goroutine leaks.
            return nil, r.err
        }
        results = append(results, r.res)
    }
    return results, nil
}

Because ch is unbuffered, if processWorkItems returns early due to an error, all remaining processWorkItem goroutines will leak. Soon after this happens, ch will become unreachable to all other goroutines not involved in the leak, allowing the runtime to detect and report the leaked goroutines.

Because this technique builds on reachability, the runtime may fail to identify leaks caused by blocking on concurrency primitives reachable through global variables or the local variables of runnable goroutines.

Special thanks to Vlad Saioc at Uber for contributing this work. The underlying theory is presented in detail in a publication by Saioc et al.

The implementation is production-ready, and is only considered an experiment for the purposes of collecting feedback on the API, specifically the choice to make it a new profile. The feature is also designed to not incur any additional run-time overhead unless it is actively in-use.

We encourage users to try out the new feature in the Go playground, in tests, in continuous integration, and in production. We welcome additional feedback on the proposal issue.

We aim to enable goroutine leak profiles by default in Go 1.27.

Compiler

The compiler can now allocate the backing store for slices on the stack in more situations, which improves performance. If this change is causing trouble, the bisect tool can be used to find the allocation causing trouble using the -compile=variablemake flag. All such new stack allocations can also be turned off using -gcflags=all=-d=variablemakehash=n. If you encounter issues with this optimization, please file an issue.

Linker

On 64-bit ARM-based Windows (the windows/arm64 port), the linker now supports internal linking mode of cgo programs, which can be requested with the -ldflags=-linkmode=internal flag.

There are several minor changes to executable files. These changes do not affect running Go programs. They may affect programs that analyze Go executables, and they may affect people who use external linking mode with custom linker scripts.

  • The moduledata structure is now in its own section, named .go.module.
  • The moduledata cutab field, which is a slice, now has the correct length; previously the length was four times too large.
  • The pcHeader found at the start of the .gopclntab section no longer records the start of the text section. That field is now always zero.
  • That pcHeader change was made so that the .gopclntab section no longer contains any relocations. On platforms that support relro, the section has moved from the relro segment to the rodata segment.
  • The funcdata symbols and the findfunctab have moved from the .rodata section to the .gopclntab section.
  • The .gosymtab section has been removed. It was previously always present but empty.
  • When using internal linking, ELF sections now appear in the section header list sorted by address. The previous order was somewhat unpredictable.

The references to section names here use the ELF names as seen on Linux and other systems. The Mach-O names as seen on Darwin start with a double underscore and do not contain any dots.

Bootstrap

As mentioned in the Go 1.24 release notes, Go 1.26 now requires Go 1.24.6 or later for bootstrap. We expect that Go 1.28 will require a minor release of Go 1.26 or later for bootstrap.

Standard library

New crypto/hpke package

The new crypto/hpke package implements Hybrid Public Key Encryption (HPKE) as specified in RFC 9180, including support for post-quantum hybrid KEMs.

New experimental simd/archsimd package

Go 1.26 introduces a new experimental simd/archsimd package, which can be enabled by setting the environment variable GOEXPERIMENT=simd at build time. This package provides access to architecture-specific SIMD operations. It is currently available on the amd64 architecture and supports 128-bit, 256-bit, and 512-bit vector types, such as Int8x16 and Float64x8, with operations such as Int8x16.Add. The API is not yet considered stable.

We intend to provide support for other architectures in future versions, but the API intentionally architecture-specific and thus non-portable. In addition, we plan to develop a high-level portable SIMD package in the future.

See the package documentation and the proposal issue for more details.

New experimental runtime/secret package

The new runtime/secret package is available as an experiment, which can be enabled by setting the environment variable GOEXPERIMENT=runtimesecret at build time. It provides a facility for securely erasing temporaries used in code that manipulates secret information—typically cryptographic in nature—such as registers, stack, new heap allocations. This package is intended to make it easier to ensure forward secrecy. It currently supports the amd64 and arm64 architectures on Linux.

Minor changes to the library

bytes

The new Buffer.Peek method returns the next n bytes from the buffer without advancing it.

crypto

The new Encapsulator and Decapsulator interfaces allow accepting abstract KEM encapsulation or decapsulation keys.

crypto/dsa

The random parameter to GenerateKey is now ignored. Instead, it now always uses a secure source of cryptographically random bytes. For deterministic testing, use the new testing/cryptotest.SetGlobalRandom function. The new GODEBUG setting cryptocustomrand=1 temporarily restores the old behavior.

crypto/ecdh

The random parameter to Curve.GenerateKey is now ignored. Instead, it now always uses a secure source of cryptographically random bytes. For deterministic testing, use the new testing/cryptotest.SetGlobalRandom function. The new GODEBUG setting cryptocustomrand=1 temporarily restores the old behavior.

The new KeyExchanger interface, implemented by PrivateKey, makes it possible to accept abstract ECDH private keys, e.g. those implemented in hardware.

crypto/ecdsa

The big.Int fields of PublicKey and PrivateKey are now deprecated.

The random parameter to GenerateKey, SignASN1, Sign, and PrivateKey.Sign is now ignored. Instead, they now always use a secure source of cryptographically random bytes. For deterministic testing, use the new testing/cryptotest.SetGlobalRandom function. The new GODEBUG setting cryptocustomrand=1 temporarily restores the old behavior.

crypto/ed25519

If the random parameter to GenerateKey is nil, GenerateKey now always uses a secure source of cryptographically random bytes, instead of crypto/rand.Reader (which could have been overridden). The new GODEBUG setting cryptocustomrand=1 temporarily restores the old behavior.

crypto/fips140

FIPS 140-3 Go Cryptographic Module v1.26.0 includes changes made to the crypto/internal/fips140/... packages up to this release, and can now be selected with GOFIPS140.

The new WithoutEnforcement and Enforced functions now allow running in GODEBUG=fips140=only mode while selectively disabling the strict FIPS 140-3 checks.

Version returns the resolved FIPS 140-3 Go Cryptographic Module version when building against a frozen module with GOFIPS140.

crypto/mlkem

The new DecapsulationKey768.Encapsulator and DecapsulationKey1024.Encapsulator methods implement the new crypto.Decapsulator interface.

Encapsulation and decapsultion operations are now approximately 18% faster.

crypto/mlkem/mlkemtest

The new crypto/mlkem/mlkemtest package exposes the Encapsulate768 and Encapsulate1024 functions which implement derandomized ML-KEM encapsulation, for use with known-answer tests.

crypto/rand

The random parameter to Prime is now ignored. Instead, it now always uses a secure source of cryptographically random bytes. For deterministic testing, use the new testing/cryptotest.SetGlobalRandom function. The new GODEBUG setting cryptocustomrand=1 temporarily restores the old behavior.

crypto/rsa

The new EncryptOAEPWithOptions function allows specifying different hash functions for OAEP padding and MGF1 mask generation.

The random parameter to GenerateKey, GenerateMultiPrimeKey, and EncryptPKCS1v15 is now ignored. Instead, they now always use a secure source of cryptographically random bytes. For deterministic testing, use the new testing/cryptotest.SetGlobalRandom function. The new GODEBUG setting cryptocustomrand=1 temporarily restores the old behavior.

If PrivateKey fields are modified after calling PrivateKey.Precompute, PrivateKey.Validate now fails.

PrivateKey.D is now checked for consistency with precomputed values, even if it is not used.

Unsafe PKCS #1 v1.5 encryption padding (implemented by EncryptPKCS1v15, DecryptPKCS1v15, and DecryptPKCS1v15SessionKey) is now deprecated.

crypto/sha3

The zero value of SHA3 is now a usable SHA3-256 instance, and the zero value of SHAKE is now a usable SHAKE256 instance.

crypto/subtle

The WithDataIndependentTiming function no longer locks the calling goroutine to the OS thread while executing the passed function. Additionally, any goroutines which are spawned during the execution of the passed function and their descendants now inherit the properties of WithDataIndependentTiming for their lifetime. This change also affects cgo in the following ways:

  • Any C code called via cgo from within the function passed to WithDataIndependentTiming, or from a goroutine spawned by the function passed to WithDataIndependentTiming and its descendants, will also have data independent timing enabled for the duration of the call. If the C code disables data independent timing, it will be re-enabled on return to Go.
  • If C code called via cgo, from the function passed to WithDataIndependentTiming or elsewhere, enables or disables data independent timing then calling into Go will preserve that state for the duration of the call.

crypto/tls

The hybrid SecP256r1MLKEM768 and SecP384r1MLKEM1024 post-quantum key exchanges are now enabled by default. They can be disabled by setting Config.CurvePreferences or with the tlssecpmlkem=0 GODEBUG setting.

The new ClientHelloInfo.HelloRetryRequest field indicates if the ClientHello was sent in response to a HelloRetryRequest message. The new ConnectionState.HelloRetryRequest field indicates if the server sent a HelloRetryRequest, or if the client received a HelloRetryRequest, depending on connection role.

The QUICConn type used by QUIC implementations includes a new event for reporting TLS handshake errors.

If Certificate.PrivateKey implements crypto.MessageSigner, its SignMessage method is used instead of Sign in TLS 1.2 and later.

The following GODEBUG settings introduced in Go 1.22 and Go 1.23 will be removed in the next major Go release. Starting in Go 1.27, the new behavior will apply regardless of GODEBUG setting or go.mod language version.

  • tlsunsafeekm: ConnectionState.ExportKeyingMaterial will require TLS 1.3 or Extended Master Secret.
  • tlsrsakex: legacy RSA-only key exchanges without ECDH won’t be enabled by default.
  • tls10server: the default minimum TLS version for both clients and servers will be TLS 1.2.
  • tls3des: the default cipher suites will not include 3DES.
  • x509keypairleaf: X509KeyPair and LoadX509KeyPair will always populate the Certificate.Leaf field.

crypto/x509

The ExtKeyUsage and KeyUsage types now have String methods that return the corresponding OID names as defined in RFC 5280 and other registries.

The ExtKeyUsage type now has an OID method that returns the corresponding OID for the EKU.

The new OIDFromASN1OID function allows converting an encoding/asn1.ObjectIdentifier into an OID.

debug/elf

Additional R_LARCH_* constants from LoongArch ELF psABI v20250521 (global version v2.40) are defined for use with LoongArch systems.

errors

The new AsType function is a generic version of As. It is type-safe, faster, and, in most cases, easier to use.

fmt

For unformatted strings, fmt.Errorf("x") now allocates less and generally matches the allocations for errors.New("x").

go/ast

The new ParseDirective function parses directive comments, which are comments such as //go:generate. Source code tools can support their own directive comments and this new API should help them implement the conventional syntax.

The new BasicLit.ValueEnd field records the precise end position of a literal so that the BasicLit.End method can now always return the correct answer. (Previously it was computed using a heuristic that was incorrect for multi-line raw string literals in Windows source files, due to removal of carriage returns.)

Programs that update the ValuePos field of BasicLit s produced by the parser may need to also update or clear the ValueEnd field to avoid minor differences in formatted output.

go/token

The new File.End convenience method returns the file’s end position.

go/types

The gotypesalias GODEBUG setting introduced in Go 1.22 will be removed in the next major Go release. Starting in Go 1.27, the go/types package will always produce an Alias type for the representation of type aliases regardless of GODEBUG setting or go.mod language version.

image/jpeg

The JPEG encoder and decoder have been replaced with new, faster, more accurate implementations. Code that expects specific bit-for-bit outputs from the encoder or decoder may need to be updated.

io

ReadAll now allocates less intermediate memory and returns a minimally sized final slice. It is often about two times faster while typically allocating around half as much total memory, with more benefit for larger inputs.

log/slog

The NewMultiHandler function creates a MultiHandler that invokes all the given Handlers. Its Enabled method reports whether any of the handlers’ Enabled methods return true. Its Handle, WithAttrs and WithGroup methods call the corresponding method on each of the enabled handlers.

net

The new Dialer methods DialIP, DialTCP, DialUDP, and DialUnix permit dialing specific network types with context values.

net/http

The new HTTP2Config.StrictMaxConcurrentRequests field controls whether a new connection should be opened if an existing HTTP/2 connection has exceeded its stream limit.

The new Transport.NewClientConn method returns a client connection to an HTTP server. Most users should continue to use Transport.RoundTrip to make requests, which manages a pool of connections. NewClientConn is useful for users who need to implement their own connection management.

Client now uses and sets cookies scoped to URLs with the host portion matching Request.Host when available. Previously, the connection address host was always used. ServeMux trailing slash redirects now use HTTP status 307 (Temporary Redirect) instead of 301 (Moved Permanently).

net/http/httptest

The HTTP client returned by Server.Client will now redirect requests for example.com and any subdomains to the server being tested.

net/http/httputil

The ReverseProxy.Director configuration field is deprecated in favor of ReverseProxy.Rewrite.

A malicious client can remove headers added by a Director function by designating those headers as hop-by-hop. Since there is no way to address this problem within the scope of the Director API, we added a new Rewrite hook in Go 1.20. Rewrite hooks are provided with both the unmodified inbound request received by the proxy and the outbound request which will be sent by the proxy.

Since the Director hook is fundamentally unsafe, we are now deprecating it.

net/netip

The new Prefix.Compare method compares two prefixes.

net/url

Parse now rejects malformed URLs containing colons in the host subcomponent, such as http://::1/ or http://localhost:80:80/. URLs containing bracketed IPv6 addresses, such as http://[::1]/ are still accepted. The new GODEBUG setting urlstrictcolons=0 restores the old behavior.

os

The new Process.WithHandle method provides access to an internal process handle on supported platforms (pidfd on Linux 5.4 or later, Handle on Windows).

On Windows, the OpenFile flag parameter can now contain any combination of Windows-specific file flags, such as FILE_FLAG_OVERLAPPED and FILE_FLAG_SEQUENTIAL_SCAN, for control of file or device caching behavior, access modes, and other special-purpose flags.

os/signal

NotifyContext now cancels the returned context with context.CancelCauseFunc and an error indicating which signal was received.

reflect

The new methods Type.Fields, Type.Methods, Type.Ins and Type.Outs return iterators for a type’s fields (for a struct type), methods, inputs and outputs parameters (for a function type), respectively.

Similarly, the new methods Value.Fields and Value.Methods return iterators over a value’s fields or methods, respectively. Each iteration yields the type information ( StructField or Method) of a field or method, along with the field or method Value.

runtime/metrics

Several new scheduler metrics have been added, including counts of goroutines in various states (waiting, runnable, etc.) under the /sched/goroutines prefix, the number of OS threads the runtime is aware of with /sched/threads:threads, and the total number of goroutines created by the program with /sched/goroutines-created:goroutines.

testing

The new methods T.ArtifactDir, B.ArtifactDir, and F.ArtifactDir return a directory in which to write test output files (artifacts).

When the -artifacts flag is provided to go test, this directory will be located under the output directory (specified with -outputdir, or the current directory by default). Otherwise, artifacts are stored in a temporary directory which is removed after the test completes.

The first call to ArtifactDir when -artifacts is provided writes the location of the directory to the test log.

For example, in a test named TestArtifacts, t.ArtifactDir() emits:

=== ARTIFACTS TestArtifacts /path/to/artifact/dir

The B.Loop method no longer prevents inlining in the loop body, which could lead to unanticipated allocation and slower benchmarks. With this fix, we expect that all benchmarks can be converted from the old B.N style to the new B.Loop style with no ill effects. Within the body of a for b.Loop() { ... } loop, function call parameters, results, and assigned variables are still kept alive, preventing the compiler from optimizing away entire parts of the benchmark.

testing/cryptotest

The new SetGlobalRandom function configures a global, deterministic cryptographic randomness source for the duration of the test. It affects crypto/rand, and all implicit sources of cryptographic randomness in the crypto/... packages.

time

The asynctimerchan GODEBUG setting introduced in Go 1.23 will be removed in the next major Go release. Starting in Go 1.27, the time package will always use unbuffered (synchronous) channels for timers regardless of GODEBUG setting or go.mod language version.

Ports

Darwin

Go 1.26 is the last release that will run on macOS 12 Monterey. Go 1.27 will require macOS 13 Ventura or later.

FreeBSD

The freebsd/riscv64 port ( GOOS=freebsd GOARCH=riscv64) has been marked broken. See issue 76475 for details.

Windows

As announced in the Go 1.25 release notes, the broken 32-bit windows/arm port ( GOOS=windows GOARCH=arm) has been removed.

PowerPC

Go 1.26 is the last release that supports the ELFv1 ABI on the big-endian 64-bit PowerPC port on Linux ( GOOS=linux GOARCH=ppc64). It will switch to the ELFv2 ABI in Go 1.27. As the port does not currently support linking against other ELF objects, we expect this change to be transparent to users.

RISC-V

The linux/riscv64 port now supports the race detector.

S390X

The s390x port now supports passing function arguments and results using registers.

WebAssembly

The compiler now unconditionally makes use of the sign extension and non-trapping floating-point to integer conversion instructions. These features have been standardized since at least Wasm 2.0. The corresponding GOWASM settings, signext and satconv, are now ignored.

For WebAssembly applications, the runtime now manages chunks of heap memory in much smaller increments, leading to significantly reduced memory usage for applications with heaps less than around 16 MiB in size.

Original source ↗

Update Oct 7, 2025 tracked by Updatify

go1.25.2 (released 2025-10-07)

go1.25.2 (released 2025-10-07) includes security fixes to the archive/tar, crypto/tls, crypto/x509, encoding/asn1, encoding/pem, net/http, net/mail, net/textproto, and net/url packages, as well as bug fixes to the compiler, the runtime, and the context, debug/pe, net/http, os, and sync/atomic packages. See the Go 1.25.2 milestone on our issue tracker for details.

Original source ↗

Update Oct 7, 2025 tracked by Updatify

go1.24.8 (released 2025-10-07)

go1.24.8 (released 2025-10-07) includes security fixes to the archive/tar, crypto/tls, crypto/x509, encoding/asn1, encoding/pem, net/http, net/mail, net/textproto, and net/url packages, as well as bug fixes to the compiler, the linker, and the debug/pe, net/http, os, and sync/atomic packages. See the Go 1.24.8 milestone on our issue tracker for details.

Original source ↗

Update Aug 12, 2025 tracked by Updatify

go1.25.0 (released 2025-08-12)

Introduction to Go 1.25

The latest Go release, version 1.25, arrives in August 2025, six months after Go 1.24. Most of its changes are in the implementation of the toolchain, runtime, and libraries. As always, the release maintains the Go 1 promise of compatibility. We expect almost all Go programs to continue to compile and run as before.

Changes to the language

There are no languages changes that affect Go programs in Go 1.25. However, in the language specification the notion of core types has been removed in favor of dedicated prose. See the respective blog post for more information.

Tools

Go command

The go build -asan option now defaults to doing leak detection at program exit. This will report an error if memory allocated by C is not freed and is not referenced by any other memory allocated by either C or Go. These new error reports may be disabled by setting ASAN_OPTIONS=detect_leaks=0 in the environment when running the program.

The Go distribution will include fewer prebuilt tool binaries. Core toolchain binaries such as the compiler and linker will still be included, but tools not invoked by build or test operations will be built and run by go tool as needed.

The new go.mod ignore directive can be used to specify directories the go command should ignore. Files in these directories and their subdirectories will be ignored by the go command when matching package patterns, such as all or ./..., but will still be included in module zip files.

The new go doc -http option will start a documentation server showing documentation for the requested object, and open the documentation in a browser window.

The new go version -m -json option will print the JSON encodings of the runtime/debug.BuildInfo structures embedded in the given Go binary files.

The go command now supports using a subdirectory of a repository as the path for a module root, when resolving a module path using the syntax <meta name="go-import" content="root-path vcs repo-url subdir"> to indicate that the root-path corresponds to the subdir of the repo-url with version control system vcs.

The new work package pattern matches all packages in the work (formerly called main) modules: either the single work module in module mode or the set of workspace modules in workspace mode.

When the go command updates the go line in a go.mod or go.work file, it no longer adds a toolchain line specifying the command’s current version.

Vet

The go vet command includes new analyzers:

Runtime

Container-aware GOMAXPROCS

The default behavior of the GOMAXPROCS has changed. In prior versions of Go, GOMAXPROCS defaults to the number of logical CPUs available at startup ( runtime.NumCPU). Go 1.25 introduces two changes:

  1. On Linux, the runtime considers the CPU bandwidth limit of the cgroup containing the process, if any. If the CPU bandwidth limit is lower than the number of logical CPUs available, GOMAXPROCS will default to the lower limit. In container runtime systems like Kubernetes, cgroup CPU bandwidth limits generally correspond to the “CPU limit” option. The Go runtime does not consider the “CPU requests” option.
  2. On all OSes, the runtime periodically updates GOMAXPROCS if the number of logical CPUs available or the cgroup CPU bandwidth limit change.

Both of these behaviors are automatically disabled if GOMAXPROCS is set manually via the GOMAXPROCS environment variable or a call to runtime.GOMAXPROCS. They can also be disabled explicitly with the GODEBUG settings containermaxprocs=0 and updatemaxprocs=0, respectively.

In order to support reading updated cgroup limits, the runtime will keep cached file descriptors for the cgroup files for the duration of the process lifetime.

New experimental garbage collector

A new garbage collector is now available as an experiment. This garbage collector’s design improves the performance of marking and scanning small objects through better locality and CPU scalability. Benchmark result vary, but we expect somewhere between a 10—40% reduction in garbage collection overhead in real-world programs that heavily use the garbage collector.

The new garbage collector may be enabled by setting GOEXPERIMENT=greenteagc at build time. We expect the design to continue to evolve and improve. To that end, we encourage Go developers to try it out and report back their experiences. See the GitHub issue for more details on the design and instructions for sharing feedback.

Trace flight recorder

Runtime execution traces have long provided a powerful, but expensive way to understand and debug the low-level behavior of an application. Unfortunately, because of their size and the cost of continuously writing an execution trace, they were generally impractical for debugging rare events.

The new runtime/trace.FlightRecorder API provides a lightweight way to capture a runtime execution trace by continuously recording the trace into an in-memory ring buffer. When a significant event occurs, a program can call FlightRecorder.WriteTo to snapshot the last few seconds of the trace to a file. This approach produces a much smaller trace by enabling applications to capture only the traces that matter.

The length of time and amount of data captured by a FlightRecorder may be configured within the FlightRecorderConfig.

Change to unhandled panic output

The message printed when a program exits due to an unhandled panic that was recovered and repanicked no longer repeats the text of the panic value.

Previously, a program which panicked with panic("PANIC"), recovered the panic, and then repanicked with the original value would print:

panic: PANIC [recovered]
  panic: PANIC

This program will now print:

panic: PANIC [recovered, repanicked]

VMA names on Linux

On Linux systems with kernel support for anonymous virtual memory area (VMA) names ( CONFIG_ANON_VMA_NAME), the Go runtime will annotate anonymous memory mappings with context about their purpose. e.g., [anon: Go: heap] for heap memory. This can be disabled with the GODEBUG setting decoratemappings=0.

Compiler

nil pointer bug

This release fixes a compiler bug, introduced in Go 1.21, that could incorrectly delay nil pointer checks. Programs like the following, which used to execute successfully (incorrectly), will now (correctly) panic with a nil-pointer exception:

package main

import "os"

func main() {
    f, err := os.Open("nonExistentFile")
    name := f.Name()
    if err != nil {
        return
    }
    println(name)
}

This program is incorrect because it uses the result of os.Open before checking the error. If err is non-nil, then the f result may be nil, in which case f.Name() should panic. However, in Go versions 1.21 through 1.24, the compiler incorrectly delayed the nil check until after the error check, causing the program to execute successfully, in violation of the Go spec. In Go 1.25, it will no longer run successfully. If this change is affecting your code, the solution is to put the non-nil error check earlier in your code, preferably immediately after the error-generating statement.

DWARF5 support

The compiler and linker in Go 1.25 now generate debug information using DWARF version 5. The newer DWARF version reduces the space required for debugging information in Go binaries, and reduces the time for linking, especially for large Go binaries. DWARF 5 generation can be disabled by setting the environment variable GOEXPERIMENT=nodwarf5 at build time (this fallback may be removed in a future Go release).

Faster slices

The compiler can now allocate the backing store for slices on the stack in more situations, which improves performance. This change has the potential to amplify the effects of incorrect unsafe.Pointer usage, see for example issue 73199. In order to track down these problems, the bisect tool can be used to find the allocation causing trouble using the -compile=variablemake flag. All such new stack allocations can also be turned off using -gcflags=all=-d=variablemakehash=n.

Linker

The linker now accepts a -funcalign=N command line option, which specifies the alignment of function entries. The default value is platform-dependent, and is unchanged in this release.

Standard library

New testing/synctest package

The new testing/synctest package provides support for testing concurrent code.

The Test function runs a test function in an isolated “bubble”. Within the bubble, time is virtualized: time package functions operate on a fake clock and the clock moves forward instantaneously if all goroutines in the bubble are blocked.

The Wait function waits for all goroutines in the current bubble to block.

This package was first available in Go 1.24 under GOEXPERIMENT=synctest, with a slightly different API. The experiment has now graduated to general availability. The old API is still present if GOEXPERIMENT=synctest is set, but will be removed in Go 1.26.

New experimental encoding/json/v2 package

Go 1.25 includes a new, experimental JSON implementation, which can be enabled by setting the environment variable GOEXPERIMENT=jsonv2 at build time.

When enabled, two new packages are available:

In addition, when the “jsonv2” GOEXPERIMENT is enabled:

  • The encoding/json package uses the new JSON implementation. Marshaling and unmarshaling behavior is unaffected, but the text of errors returned by package function may change.
  • The encoding/json package contains a number of new options which may be used to configure the marshaler and unmarshaler.

The new implementation performs substantially better than the existing one under many scenarios. In general, encoding performance is at parity between the implementations and decoding is substantially faster in the new one. See the github.com/go-json-experiment/jsonbench repository for more detailed analysis.

See the proposal issue for more details.

We encourage users of encoding/json to test their programs with GOEXPERIMENT=jsonv2 enabled to help detect any compatibility issues with the new implementation.

We expect the design of encoding/json/v2 to continue to evolve. We encourage developers to try out the new API and provide feedback on the proposal issue.

Minor changes to the library

archive/tar

The Writer.AddFS implementation now supports symbolic links for filesystems that implement io/fs.ReadLinkFS.

encoding/asn1

Unmarshal and UnmarshalWithParams now parse the ASN.1 types T61String and BMPString more consistently. This may result in some previously accepted malformed encodings now being rejected.

crypto

MessageSigner is a new signing interface that can be implemented by signers that wish to hash the message to be signed themselves. A new function is also introduced, SignMessage, which attempts to upgrade a Signer interface to MessageSigner, using the MessageSigner.SignMessage method if successful, and Signer.Sign if not. This can be used when code wishes to support both Signer and MessageSigner.

Changing the fips140 GODEBUG setting after the program has started is now a no-op. Previously, it was documented as not allowed, and could cause a panic if changed.

SHA-1, SHA-256, and SHA-512 are now slower on amd64 when AVX2 instructions are not available. All server processors (and most others) produced since 2015 support AVX2.

crypto/ecdsa

The new ParseRawPrivateKey, ParseUncompressedPublicKey, PrivateKey.Bytes, and PublicKey.Bytes functions and methods implement low-level encodings, replacing the need to use crypto/elliptic or math/big functions and methods.

When FIPS 140-3 mode is enabled, signing is now four times faster, matching the performance of non-FIPS mode.

crypto/ed25519

When FIPS 140-3 mode is enabled, signing is now four times faster, matching the performance of non-FIPS mode.

crypto/elliptic

The hidden and undocumented Inverse and CombinedMult methods on some Curve implementations have been removed.

crypto/rsa

PublicKey no longer claims that the modulus value is treated as secret. VerifyPKCS1v15 and VerifyPSS already warned that all inputs are public and could be leaked, and there are mathematical attacks that can recover the modulus from other public values.

Key generation is now three times faster.

crypto/sha1

Hashing is now two times faster on amd64 when SHA-NI instructions are available.

crypto/sha3

The new SHA3.Clone method implements hash.Cloner.

Hashing is now two times faster on Apple M processors.

crypto/tls

The new ConnectionState.CurveID field exposes the key exchange mechanism used to establish the connection.

The new Config.GetEncryptedClientHelloKeys callback can be used to set the EncryptedClientHelloKey s for a server to use when a client sends an Encrypted Client Hello extension.

SHA-1 signature algorithms are now disallowed in TLS 1.2 handshakes, per RFC 9155. They can be re-enabled with the GODEBUG setting tlssha1=1.

When FIPS 140-3 mode is enabled, Extended Master Secret is now required in TLS 1.2, and Ed25519 and X25519MLKEM768 are now allowed.

TLS servers now prefer the highest supported protocol version, even if it isn’t the client’s most preferred protocol version.

Both TLS clients and servers are now stricter in following the specifications and in rejecting off-spec behavior. Connections with compliant peers should be unaffected.

crypto/x509

CreateCertificate, CreateCertificateRequest, and CreateRevocationList can now accept a crypto.MessageSigner signing interface as well as crypto.Signer. This allows these functions to use signers which implement “one-shot” signing interfaces, where hashing is done as part of the signing operation, instead of by the caller.

CreateCertificate now uses truncated SHA-256 to populate the SubjectKeyId if it is missing. The GODEBUG setting x509sha256skid=0 reverts to SHA-1.

ParseCertificate now rejects certificates which contain a BasicConstraints extension that contains a negative pathLenConstraint.

ParseCertificate now handles strings encoded with the ASN.1 T61String and BMPString types more consistently. This may result in some previously accepted malformed encodings now being rejected.

debug/elf

The debug/elf package adds two new constants:

go/ast

The FilterPackage, PackageExports, and MergePackageFiles functions, and the MergeMode type and its constants, are all deprecated, as they are for use only with the long-deprecated Object and Package machinery.

The new PreorderStack function, like Inspect, traverses a syntax tree and provides control over descent into subtrees, but as a convenience it also provides the stack of enclosing nodes at each point.

go/parser

The ParseDir function is deprecated.

go/token

The new FileSet.AddExistingFiles method enables existing File s to be added to a FileSet, or a FileSet to be constructed for an arbitrary set of File s, alleviating the problems associated with a single global FileSet in long-lived applications.

go/types

Var now has a Var.Kind method that classifies the variable as one of: package-level, receiver, parameter, result, local variable, or a struct field.

The new LookupSelection function looks up the field or method of a given name and receiver type, like the existing LookupFieldOrMethod function, but returns the result in the form of a Selection.

hash

The new XOF interface can be implemented by “extendable output functions”, which are hash functions with arbitrary or unlimited output length such as SHAKE.

Hashes implementing the new Cloner interface can return a copy of their state. All standard library Hash implementations now implement Cloner.

hash/maphash

The new Hash.Clone method implements hash.Cloner.

io/fs

A new ReadLinkFS interface provides the ability to read symbolic links in a filesystem.

log/slog

GroupAttrs creates a group Attr from a slice of Attr values.

Record now has a Source method, returning its source location or nil if unavailable.

mime/multipart

The new helper function FileContentDisposition builds multipart Content-Disposition header fields.

net

LookupMX and Resolver.LookupMX now return DNS names that look like valid IP address, as well as valid domain names. Previously if a name server returned an IP address as a DNS name, LookupMX would discard it, as required by the RFCs. However, name servers in practice do sometimes return IP addresses.

On Windows, ListenMulticastUDP now supports IPv6 addresses.

On Windows, it is now possible to convert between an os.File and a network connection. Specifically, the FileConn, FilePacketConn, and FileListener functions are now implemented, and return a network connection or listener corresponding to an open file. Similarly, the File methods of TCPConn, UDPConn, UnixConn, IPConn, TCPListener, and UnixListener are now implemented, and return the underlying os.File of a network connection.

net/http

The new CrossOriginProtection implements protections against Cross-Site Request Forgery (CSRF) by rejecting non-safe cross-origin browser requests. It uses modern browser Fetch metadata, doesn’t require tokens or cookies, and supports origin-based and pattern-based bypasses.

os

On Windows, NewFile now supports handles opened for asynchronous I/O (that is, syscall.FILE_FLAG_OVERLAPPED is specified in the syscall.CreateFile call). These handles are associated with the Go runtime’s I/O completion port, which provides the following benefits for the resulting File:

This enhancement is especially beneficial for applications that communicate via named pipes on Windows.

Note that a handle can only be associated with one completion port at a time. If the handle provided to NewFile is already associated with a completion port, the returned File is downgraded to synchronous I/O mode. In this case, I/O methods will block an OS thread, and the deadline methods have no effect.

The filesystems returned by DirFS and Root.FS implement the new io/fs.ReadLinkFS interface. CopyFS supports symlinks when copying filesystems that implement io/fs.ReadLinkFS.

The Root type supports the following additional methods:

reflect

The new TypeAssert function permits converting a Value directly to a Go value of the given type. This is like using a type assertion on the result of Value.Interface, but avoids unnecessary memory allocations.

regexp/syntax

The \p{name} and \P{name} character class syntaxes now accept the names Any, ASCII, Assigned, Cn, and LC, as well as Unicode category aliases like \p{Letter} for \pL. Following Unicode TR18, they also now use case-insensitive name lookups, ignoring spaces, underscores, and hyphens.

runtime

Cleanup functions scheduled by AddCleanup are now executed concurrently and in parallel, making cleanups more viable for heavy use like the unique package. Note that individual cleanups should still shunt their work to a new goroutine if they must execute or block for a long time to avoid blocking the cleanup queue.

A new GODEBUG=checkfinalizers=1 setting helps find common issues with finalizers and cleanups, such as those described in the GC guide. In this mode, the runtime runs diagnostics on each garbage collection cycle, and will also regularly report the finalizer and cleanup queue lengths to stderr to help identify issues with long-running finalizers and/or cleanups. See the GODEBUG documentation for more details.

The new SetDefaultGOMAXPROCS function sets GOMAXPROCS to the runtime default value, as if the GOMAXPROCS environment variable is not set. This is useful for enabling the new GOMAXPROCS default if it has been disabled by the GOMAXPROCS environment variable or a prior call to GOMAXPROCS.

runtime/pprof

The mutex profile for contention on runtime-internal locks now correctly points to the end of the critical section that caused the delay. This matches the profile’s behavior for contention on sync.Mutex values. The runtimecontentionstacks setting for GODEBUG, which allowed opting in to the unusual behavior of Go 1.22 through 1.24 for this part of the profile, is now gone.

sync

The new WaitGroup.Go method makes the common pattern of creating and counting goroutines more convenient.

testing

The new methods T.Attr, B.Attr, and F.Attr emit an attribute to the test log. An attribute is an arbitrary key and value associated with a test.

For example, in a test named TestF, t.Attr("key", "value") emits:

=== ATTR  TestF key value

With the -json flag, attributes appear as a new “attr” action.

The new Output method of T, B and F provides an io.Writer that writes to the same test output stream as TB.Log. Like TB.Log, the output is indented, but it does not include the file and line number.

The AllocsPerRun function now panics if parallel tests are running. The result of AllocsPerRun is inherently flaky if other tests are running. The new panicking behavior helps catch such bugs.

testing/fstest

MapFS implements the new io/fs.ReadLinkFS interface. TestFS will verify the functionality of the io/fs.ReadLinkFS interface if implemented. TestFS will no longer follow symlinks to avoid unbounded recursion.

unicode

The new CategoryAliases map provides access to category alias names, such as “Letter” for “L”.

The new categories Cn and LC define unassigned codepoints and cased letters, respectively. These have always been defined by Unicode but were inadvertently omitted in earlier versions of Go. The C category now includes Cn, meaning it has added all unassigned code points.

unique

The unique package now reclaims interned values more eagerly, more efficiently, and in parallel. As a consequence, applications using Make are now less likely to experience memory blow-up when lots of truly unique values are interned.

Values passed to Make containing Handle s previously required multiple garbage collection cycles to collect, proportional to the depth of the chain of Handle values. Now, once unused, they are collected promptly in a single cycle.

Ports

Darwin

As announced in the Go 1.24 release notes, Go 1.25 requires macOS 12 Monterey or later. Support for previous versions has been discontinued.

Windows

Go 1.25 is the last release that contains the broken 32-bit windows/arm port ( GOOS=windows GOARCH=arm). It will be removed in Go 1.26.

AMD64

In GOAMD64=v3 mode or higher, the compiler will now use fused multiply-add instructions to make floating-point arithmetic faster and more accurate. This may change the exact floating-point values that a program generates.

To avoid fusing use an explicit float64 cast, like float64(a*b)+c.

Loong64

The linux/loong64 port now supports the race detector, gathering traceback information from C code using runtime.SetCgoTraceback, and linking cgo programs with the internal link mode.

RISC-V

The linux/riscv64 port now supports the plugin build mode.

The GORISCV64 environment variable now accepts a new value rva23u64, which selects the RVA23U64 user-mode application profile.

Original source ↗

Update Feb 11, 2025 tracked by Updatify

go1.24.0 (released 2025-02-11)

Introduction to Go 1.24

The latest Go release, version 1.24, arrives in February 2025, six months after Go 1.23. Most of its changes are in the implementation of the toolchain, runtime, and libraries. As always, the release maintains the Go 1 promise of compatibility. We expect almost all Go programs to continue to compile and run as before.

Changes to the language

Go 1.24 now fully supports generic type aliases: a type alias may be parameterized like a defined type. See the language spec for details. For now, the feature can be disabled by setting GOEXPERIMENT=noaliastypeparams; but the aliastypeparams setting will be removed for Go 1.25.

Tools

Go command

Go modules can now track executable dependencies using tool directives in go.mod. This removes the need for the previous workaround of adding tools as blank imports to a file conventionally named “tools.go”. The go tool command can now run these tools in addition to tools shipped with the Go distribution. For more information see the documentation.

The new -tool flag for go get causes a tool directive to be added to the current module for named packages in addition to adding require directives.

The new tool meta-pattern refers to all tools in the current module. This can be used to upgrade them all with go get tool or to install them into your GOBIN directory with go install tool.

Executables created by go run and the new behavior of go tool are now cached in the Go build cache. This makes repeated executions faster at the expense of making the cache larger. See #69290.

The go build and go install commands now accept a -json flag that reports build output and failures as structured JSON output on standard output. For details of the reporting format, see go help buildjson.

Furthermore, go test -json now reports build output and failures in JSON, interleaved with test result JSON. These are distinguished by new Action types, but if they cause problems in a test integration system, you can revert to the text build output with GODEBUG setting gotestjsonbuildtext=1.

The new GOAUTH environment variable provides a flexible way to authenticate private module fetches. See go help goauth for more information.

The go build command now sets the main module’s version in the compiled binary based on the version control system tag and/or commit. A +dirty suffix will be appended if there are uncommitted changes. Use the -buildvcs=false flag to omit version control information from the binary.

The new GODEBUG setting toolchaintrace=1 can be used to trace the go command’s toolchain selection process.

Cgo

Cgo supports new annotations for C functions to improve run time performance. #cgo noescape cFunctionName tells the compiler that memory passed to the C function cFunctionname does not escape. #cgo nocallback cFunctionName tells the compiler that the C function cFunctionName does not call back to any Go functions. For more information, see the cgo documentation.

Cgo currently refuses to compile calls to a C function which has multiple incompatible declarations. For instance, if f is declared as both void f(int) and void f(double), cgo will report an error instead of possibly generating an incorrect call sequence for f(0). New in this release is a better detector for this error condition when the incompatible declarations appear in different files. See #67699.

Objdump

The objdump tool now supports dissassembly on 64-bit LoongArch ( GOARCH=loong64), RISC-V ( GOARCH=riscv64), and S390X ( GOARCH=s390x).

Vet

The new tests analyzer reports common mistakes in declarations of tests, fuzzers, benchmarks, and examples in test packages, such as malformed names, incorrect signatures, or examples that document non-existent identifiers. Some of these mistakes may cause tests not to run. This analyzer is among the subset of analyzers that are run by go test.

The existing printf analyzer now reports a diagnostic for calls of the form fmt.Printf(s), where s is a non-constant format string, with no other arguments. Such calls are nearly always a mistake as the value of s may contain the % symbol; use fmt.Print instead. See #60529. This check tends to produce findings in existing code, and so is only applied when the language version (as specified by the go.mod go directive or //go:build comments) is at least Go 1.24, to avoid causing continuous integration failures when updating to the 1.24 Go toolchain.

The existing buildtag analyzer now reports a diagnostic when there is an invalid Go major version build constraint within a //go:build directive. For example, //go:build go1.23.1 refers to a point release; use //go:build go1.23 instead. See #64127.

The existing copylock analyzer now reports a diagnostic when a variable declared in a 3-clause “for” loop such as for i := iter(); done(i); i = next(i) { ... } contains a sync.Locker, such as a sync.Mutex. Go 1.22 changed the behavior of these loops to create a new variable for each iteration, copying the value from the previous iteration; this copy operation is not safe for locks. See #66387.

GOCACHEPROG

The cmd/go internal binary and test caching mechanism can now be implemented by child processes implementing a JSON protocol between the cmd/go tool and the child process named by the GOCACHEPROG environment variable. This was previously behind a GOEXPERIMENT. For protocol details, see the documentation.

Runtime

Several performance improvements to the runtime have decreased CPU overheads by 2–3% on average across a suite of representative benchmarks. Results may vary by application. These improvements include a new builtin map implementation based on Swiss Tables, more efficient memory allocation of small objects, and a new runtime-internal mutex implementation.

The new builtin map implementation and new runtime-internal mutex may be disabled by setting GOEXPERIMENT=noswissmap and GOEXPERIMENT=nospinbitmutex at build time respectively.

Compiler

The compiler already disallowed defining new methods with receiver types that were cgo-generated, but it was possible to circumvent that restriction via an alias type. Go 1.24 now always reports an error if a receiver denotes a cgo-generated type, whether directly or indirectly (through an alias type).

Linker

The linker now generates a GNU build ID (the ELF NT_GNU_BUILD_ID note) on ELF platforms and a UUID (the Mach-O LC_UUID load command) on macOS by default. The build ID or UUID is derived from the Go build ID. It can be disabled by the -B none linker flag, or overridden by the -B 0xNNNN linker flag with a user-specified hexadecimal value.

Bootstrap

As mentioned in the Go 1.22 release notes, Go 1.24 now requires Go 1.22.6 or later for bootstrap. We expect that Go 1.26 will require a point release of Go 1.24 or later for bootstrap.

Standard library

Directory-limited filesystem access

The new os.Root type provides the ability to perform filesystem operations within a specific directory.

The os.OpenRoot function opens a directory and returns an os.Root. Methods on os.Root operate within the directory and do not permit paths that refer to locations outside the directory, including ones that follow symbolic links out of the directory. The methods on os.Root mirror most of the file system operations available in the os package, including for example os.Root.Open, os.Root.Create, os.Root.Mkdir, and os.Root.Stat,

New benchmark function

Benchmarks may now use the faster and less error-prone testing.B.Loop method to perform benchmark iterations like for b.Loop() { ... } in place of the typical loop structures involving b.N like for range b.N. This offers two significant advantages:

  • The benchmark function will execute exactly once per -count, so expensive setup and cleanup steps execute only once.
  • Function call parameters and results are kept alive, preventing the compiler from fully optimizing away the loop body.

Improved finalizers

The new runtime.AddCleanup function is a finalization mechanism that is more flexible, more efficient, and less error-prone than runtime.SetFinalizer. AddCleanup attaches a cleanup function to an object that will run once the object is no longer reachable. However, unlike SetFinalizer, multiple cleanups may be attached to a single object, cleanups may be attached to interior pointers, cleanups do not generally cause leaks when objects form a cycle, and cleanups do not delay the freeing of an object or objects it points to. New code should prefer AddCleanup over SetFinalizer.

New weak package

The new weak package provides weak pointers.

Weak pointers are a low-level primitive provided to enable the creation of memory-efficient structures, such as weak maps for associating values, canonicalization maps for anything not covered by package unique, and various kinds of caches. For supporting these use-cases, this release also provides runtime.AddCleanup and maphash.Comparable.

New crypto/mlkem package

The new crypto/mlkem package implements ML-KEM-768 and ML-KEM-1024.

ML-KEM is a post-quantum key exchange mechanism formerly known as Kyber and specified in FIPS 203.

New crypto/hkdf, crypto/pbkdf2, and crypto/sha3 packages

The new crypto/hkdf package implements the HMAC-based Extract-and-Expand key derivation function HKDF, as defined in RFC 5869.

The new crypto/pbkdf2 package implements the password-based key derivation function PBKDF2, as defined in RFC 8018.

The new crypto/sha3 package implements the SHA-3 hash function and SHAKE and cSHAKE extendable-output functions, as defined in FIPS 202.

All three packages are based on pre-existing golang.org/x/crypto/... packages.

FIPS 140-3 compliance

This release includes a new set of mechanisms to facilitate FIPS 140-3 compliance.

The Go Cryptographic Module is a set of internal standard library packages that are transparently used to implement FIPS 140-3 approved algorithms. Applications require no changes to use the Go Cryptographic Module for approved algorithms.

The new GOFIPS140 environment variable can be used to select the Go Cryptographic Module version to use in a build. The new fips140 GODEBUG setting can be used to enable FIPS 140-3 mode at runtime.

Go 1.24 includes Go Cryptographic Module version v1.0.0, which is currently under test with a CMVP-accredited laboratory.

New experimental testing/synctest package

The new experimental testing/synctest package provides support for testing concurrent code.

  • The synctest.Run function starts a group of goroutines in an isolated “bubble”. Within the bubble, time package functions operate on a fake clock.
  • The synctest.Wait function waits for all goroutines in the current bubble to block.

See the package documentation for more details.

The synctest package is experimental and must be enabled by setting GOEXPERIMENT=synctest at build time. The package API is subject to change in future releases. See issue #67434 for more information and to provide feeback.

Minor changes to the library

archive

The (*Writer).AddFS implementations in both archive/zip and archive/tar now write a directory header for an empty directory.

bytes

The bytes package adds several functions that work with iterators:

  • Lines returns an iterator over the newline-terminated lines in a byte slice.
  • SplitSeq returns an iterator over all subslices of a byte slice split around a separator.
  • SplitAfterSeq returns an iterator over subslices of a byte slice split after each instance of a separator.
  • FieldsSeq returns an iterator over subslices of a byte slice split around runs of whitespace characters, as defined by unicode.IsSpace.
  • FieldsFuncSeq returns an iterator over subslices of a byte slice split around runs of Unicode code points satisfying a predicate.

crypto/aes

The value returned by NewCipher no longer implements the NewCTR, NewGCM, NewCBCEncrypter, and NewCBCDecrypter methods. These methods were undocumented and not available on all architectures. Instead, the Block value should be passed directly to the relevant crypto/cipher functions. For now, crypto/cipher still checks for those methods on Block values, even if they are not used by the standard library anymore.

crypto/cipher

The new NewGCMWithRandomNonce function returns an AEAD that implements AES-GCM by generating a random nonce during Seal and prepending it to the ciphertext.

The Stream implementation returned by NewCTR when used with crypto/aes is now several times faster on amd64 and arm64.

NewOFB, NewCFBEncrypter, and NewCFBDecrypter are now deprecated. OFB and CFB mode are not authenticated, which generally enables active attacks to manipulate and recover the plaintext. It is recommended that applications use AEAD modes instead. If an unauthenticated Stream mode is required, use NewCTR instead.

crypto/ecdsa

PrivateKey.Sign now produces a deterministic signature according to RFC 6979 if the random source is nil.

crypto/md5

The value returned by md5.New now also implements the encoding.BinaryAppender interface.

crypto/rand

The Read function is now guaranteed not to fail. It will always return nil as the error result. If Read were to encounter an error while reading from Reader, the program will irrecoverably crash. Note that the platform APIs used by the default Reader are documented to always succeed, so this change should only affect programs that override the Reader variable. One exception are Linux kernels before version 3.17, where the default Reader still opens /dev/urandom and may fail.

On Linux 6.11 and later, Reader now uses the getrandom system call via vDSO. This is several times faster, especially for small reads.

On OpenBSD, Reader now uses arc4random_buf(3).

The new Text function can be used to generate cryptographically secure random text strings.

crypto/rsa

GenerateKey now returns an error if a key of less than 1024 bits is requested. All Sign, Verify, Encrypt, and Decrypt methods now return an error if used with a key smaller than 1024 bits. Such keys are insecure and should not be used. GODEBUG setting rsa1024min=0 restores the old behavior, but we recommend doing so only if necessary and only in tests, for example by adding a //go:debug rsa1024min=0 line to a test file. A new GenerateKey example provides an easy-to-use standard 2048-bit test key.

It is now safe and more efficient to call PrivateKey.Precompute before PrivateKey.Validate. Precompute is now faster in the presence of partially filled out PrecomputedValues, such as when unmarshaling a key from JSON.

The package now rejects more invalid keys, even when Validate is not called, and GenerateKey may return new errors for broken random sources. The Primes and Precomputed fields of PrivateKey are now used and validated even when some values are missing. See also the changes to crypto/x509 parsing and marshaling of RSA keys described below.

SignPKCS1v15 and VerifyPKCS1v15 now support SHA-512/224, SHA-512/256, and SHA-3.

GenerateKey now uses a slightly different method to generate the private exponent (Carmichael’s totient instead of Euler’s totient). Rare applications that externally regenerate keys from only the prime factors may produce different but compatible results.

Public and private key operations are now up to two times faster on wasm.

crypto/sha1

The value returned by sha1.New now also implements the encoding.BinaryAppender interface.

crypto/sha256

The values returned by sha256.New and sha256.New224 now also implement the encoding.BinaryAppender interface.

crypto/sha512

The values returned by sha512.New, sha512.New384, sha512.New512_224 and sha512.New512_256 now also implement the encoding.BinaryAppender interface.

crypto/subtle

The new WithDataIndependentTiming function allows the user to run a function with architecture specific features enabled which guarantee specific instructions are data value timing invariant. This can be used to make sure that code designed to run in constant time is not optimized by CPU-level features such that it operates in variable time. Currently, WithDataIndependentTiming uses the PSTATE.DIT bit on arm64, and is a no-op on all other architectures. GODEBUG setting dataindependenttiming=1 enables the DIT mode for the entire Go program.

The XORBytes output must overlap exactly or not at all with the inputs. Previously, the behavior was otherwise undefined, while now XORBytes will panic.

crypto/tls

The TLS server now supports Encrypted Client Hello (ECH). This feature can be enabled by populating the Config.EncryptedClientHelloKeys field.

The new post-quantum X25519MLKEM768 key exchange mechanism is now supported and is enabled by default when Config.CurvePreferences is nil. GODEBUG setting tlsmlkem=0 reverts the default. This can be useful when dealing with buggy TLS servers that do not handle large records correctly, causing a timeout during the handshake (see TLS post-quantum TL;DR fail).

Support for the experimental X25519Kyber768Draft00 key exchange has been removed.

Key exchange ordering is now handled entirely by the crypto/tls package. The order of Config.CurvePreferences is now ignored, and the contents are only used to determine which key exchanges to enable when the field is populated.

The new ClientHelloInfo.Extensions field lists the IDs of the extensions received in the Client Hello message. This can be useful for fingerprinting TLS clients.

crypto/x509

The x509sha1 GODEBUG setting has been removed. Certificate.Verify no longer supports SHA-1 based signatures.

OID now implements the encoding.BinaryAppender and encoding.TextAppender interfaces.

The default certificate policies field has changed from Certificate.PolicyIdentifiers to Certificate.Policies. When parsing certificates, both fields will be populated, but when creating certificates policies will now be taken from the Certificate.Policies field instead of the Certificate.PolicyIdentifiers field. This change can be reverted with GODEBUG setting x509usepolicies=0.

CreateCertificate will now generate a serial number using a RFC 5280 compliant method when passed a template with a nil Certificate.SerialNumber field, instead of failing.

Certificate.Verify now supports policy validation, as defined in RFC 5280 and RFC 9618. The new VerifyOptions.CertificatePolicies field can be set to an acceptable set of policy OIDs. Only certificate chains with valid policy graphs will be returned from Certificate.Verify.

MarshalPKCS8PrivateKey now returns an error instead of marshaling an invalid RSA key. ( MarshalPKCS1PrivateKey doesn’t have an error return, and its behavior when provided invalid keys continues to be undefined.)

ParsePKCS1PrivateKey and ParsePKCS8PrivateKey now use and validate the encoded CRT values, so might reject invalid RSA keys that were previously accepted. Use GODEBUG setting x509rsacrt=0 to revert to recomputing the CRT values.

debug/elf

The debug/elf package adds support for handling symbol versions in dynamic ELF (Executable and Linkable Format) files. The new File.DynamicVersions method returns a list of dynamic versions defined in the ELF file. The new File.DynamicVersionNeeds method returns a list of dynamic versions required by this ELF file that are defined in other ELF objects. Finally, the new Symbol.HasVersion and Symbol.VersionIndex fields indicate the version of a symbol.

encoding

Two new interfaces, TextAppender and BinaryAppender, have been introduced to append the textual or binary representation of an object to a byte slice. These interfaces provide the same functionality as TextMarshaler and BinaryMarshaler, but instead of allocating a new slice each time, they append the data directly to an existing slice. These interfaces are now implemented by standard library types that already implemented TextMarshaler and/or BinaryMarshaler.

encoding/json

When marshaling, a struct field with the new omitzero option in the struct field tag will be omitted if its value is zero. If the field type has an IsZero() bool method, that will be used to determine whether the value is zero. Otherwise, the value is zero if it is the zero value for its type. The omitzero field tag is clearer and less error-prone than omitempty when the intent is to omit zero values. In particular, unlike omitempty, omitzero omits zero-valued time.Time values, which is a common source of friction.

If both omitempty and omitzero are specified, the field will be omitted if the value is either empty or zero (or both).

UnmarshalTypeError.Field now includes embedded structs to provide more detailed error messages.

go/types

All go/types data structures that expose sequences using a pair of methods such as Len() int and At(int) T now also have methods that return iterators, allowing you to simplify code such as this:

params := fn.Type.(*types.Signature).Params()
for i := 0; i < params.Len(); i++ {
   use(params.At(i))
}

to this:

for param := range fn.Signature().Params().Variables() {
   use(param)
}

The methods are: Interface.EmbeddedTypes, Interface.ExplicitMethods, Interface.Methods, MethodSet.Methods, Named.Methods, Scope.Children, Struct.Fields, Tuple.Variables, TypeList.Types, TypeParamList.TypeParams, Union.Terms.

hash/adler32

The value returned by New now also implements the encoding.BinaryAppender interface.

hash/crc32

The values returned by New and NewIEEE now also implement the encoding.BinaryAppender interface.

hash/crc64

The value returned by New now also implements the encoding.BinaryAppender interface.

hash/fnv

The values returned by New32, New32a, New64, New64a, New128 and New128a now also implement the encoding.BinaryAppender interface.

hash/maphash

The new Comparable and WriteComparable functions can compute the hash of any comparable value. These make it possible to hash anything that can be used as a Go map key.

log/slog

The new DiscardHandler is a handler that is never enabled and always discards its output.

Level and LevelVar now implement the encoding.TextAppender interface.

math/big

Float, Int and Rat now implement the encoding.TextAppender interface.

math/rand

Calls to the deprecated top-level Seed function no longer have any effect. To restore the old behavior use GODEBUG setting randseednop=0. For more background see proposal #67273.

math/rand/v2

ChaCha8 and PCG now implement the encoding.BinaryAppender interface.

net

ListenConfig now uses MPTCP by default on systems where it is supported (currently on Linux only).

IP now implements the encoding.TextAppender interface.

net/http

Transport ’s limit on 1xx informational responses received in response to a request has changed. It previously aborted a request and returned an error after receiving more than 5 1xx responses. It now returns an error if the total size of all 1xx responses exceeds the Transport.MaxResponseHeaderBytes configuration setting.

In addition, when a request has a net/http/httptrace.ClientTrace.Got1xxResponse trace hook, there is now no limit on the total number of 1xx responses. The Got1xxResponse hook may return an error to abort a request.

Transport and Server now have an HTTP2 field which permits configuring HTTP/2 protocol settings.

The new Server.Protocols and Transport.Protocols fields provide a simple way to configure what HTTP protocols a server or client use.

The server and client may be configured to support unencrypted HTTP/2 connections.

When Server.Protocols contains UnencryptedHTTP2, the server will accept HTTP/2 connections on unencrypted ports. The server can accept both HTTP/1 and unencrypted HTTP/2 on the same port.

When Transport.Protocols contains UnencryptedHTTP2 and does not contain HTTP1, the transport will use unencrypted HTTP/2 for http:// URLs. If the transport is configured to use both HTTP/1 and unencrypted HTTP/2, it will use HTTP/1.

Unencrypted HTTP/2 support uses “HTTP/2 with Prior Knowledge” (RFC 9113, section 3.3). The deprecated “Upgrade: h2c” header is not supported.

net/netip

Addr, AddrPort and Prefix now implement the encoding.BinaryAppender and encoding.TextAppender interfaces.

net/url

URL now also implements the encoding.BinaryAppender interface.

os/user

On Windows, Current can now be used in Windows Nano Server. The implementation has been updated to avoid using functions from the NetApi32 library, which is not available in Nano Server.

On Windows, Current, Lookup and LookupId now support the following built-in service user accounts:

  • NT AUTHORITY\SYSTEM
  • NT AUTHORITY\LOCAL SERVICE
  • NT AUTHORITY\NETWORK SERVICE

On Windows, Current has been made considerably faster when the current user is joined to a slow domain, which is the usual case for many corporate users. The new implementation performance is now in the order of milliseconds, compared to the previous implementation which could take several seconds, or even minutes, to complete.

On Windows, Current now returns the process owner user when the current thread is impersonating another user. Previously, it returned an error.

regexp

Regexp now implements the encoding.TextAppender interface.

runtime

The GOROOT function is now deprecated. In new code prefer to use the system path to locate the “go” binary, and use go env GOROOT to find its GOROOT.

strings

The strings package adds several functions that work with iterators:

  • Lines returns an iterator over the newline-terminated lines in a string.
  • SplitSeq returns an iterator over all substrings of a string split around a separator.
  • SplitAfterSeq returns an iterator over substrings of a string split after each instance of a separator.
  • FieldsSeq returns an iterator over substrings of a string split around runs of whitespace characters, as defined by unicode.IsSpace.
  • FieldsFuncSeq returns an iterator over substrings of a string split around runs of Unicode code points satisfying a predicate.

sync

The implementation of sync.Map has been changed, improving performance, particularly for map modifications. For instance, modifications of disjoint sets of keys are much less likely to contend on larger maps, and there is no longer any ramp-up time required to achieve low-contention loads from the map.

If you encounter any problems, set GOEXPERIMENT=nosynchashtriemap at build time to switch back to the old implementation and please file an issue.

testing

The new T.Context and B.Context methods return a context that’s canceled after the test completes and before test cleanup functions run.

The new T.Chdir and B.Chdir methods can be used to change the working directory for the duration of a test or benchmark.

text/template

Templates now support range-over-func and range-over-int.

time

Time now implements the encoding.BinaryAppender and encoding.TextAppender interfaces.

Ports

Linux

As announced in the Go 1.23 release notes, Go 1.24 requires Linux kernel version 3.2 or later.

Darwin

Go 1.24 is the last release that will run on macOS 11 Big Sur. Go 1.25 will require macOS 12 Monterey or later.

WebAssembly

The go:wasmexport compiler directive is added for Go programs to export functions to the WebAssembly host.

On WebAssembly System Interface Preview 1 ( GOOS=wasip1 GOARCH=wasm), Go 1.24 supports building a Go program as a reactor/library, by specifying the -buildmode=c-shared build flag.

More types are now permitted as argument or result types for go:wasmimport functions. Specifically, bool, string, uintptr, and pointers to certain types are allowed (see the documentation for detail), along with 32-bit and 64-bit integer and float types, and unsafe.Pointer, which are already allowed. These types are also permitted as argument or result types for go:wasmexport functions.

The support files for WebAssembly have been moved to lib/wasm from misc/wasm.

The initial memory size is significantly reduced, especially for small WebAssembly applications.

Windows

The 32-bit windows/arm port ( GOOS=windows GOARCH=arm) has been marked broken. See issue #70705 for details.

Original source ↗

Update Sep 5, 2024 tracked by Updatify

go1.23.1 (released 2024-09-05)

go1.23.1 (released 2024-09-05) includes security fixes to the encoding/gob, go/build/constraint, and go/parser packages, as well as bug fixes to the compiler, the go command, the runtime, and the database/sql, go/types, os, runtime/trace, and unique packages. See the Go 1.23.1 milestone on our issue tracker for details.

Original source ↗