Go 1 23

Go 1.23

This overview applies when the project's target Go version is at least 1.23.

Language

• Available capability: range-over-function iterators for pull-free sequence APIs whose shape is func(func() bool), func(func(K) bool), or func(func(K, V) bool). Stop producing values when the yield function returns false.
• GOEXPERIMENT=aliastypeparams is an experimental opt-in for evaluate generic type aliases within one package. Do not design cross-package APIs around them in Go 1.23.

Tools

• Available capability: go mod tidy -diff in checks that must report required module-file changes without modifying files.
• go env -changed can inspect only environment settings that differ from Go's defaults.
• go vet can detect standard-library symbols newer than the effective Go version declared by go.mod or file build constraints.
• uploaded toolchain telemetry is opt-in. Use go telemetry local to retain counters locally or go telemetry on only with an explicit project or user decision.
• Unsupported or discouraged: add new //go:linkname references to unmarked standard-library internals. Use -checklinkname=0 only for debugging or experiments.

Iterators and canonical values

• Define iterator APIs with iter.Seq or iter.Seq2, and consume them directly with range.
• Modern alternative: the iterator operations in slices and maps when they avoid intermediate collections. Use Collect, Sorted, or maps.Collect when a materialised result is actually needed.
• unique.Make is available when many equal comparable values should share canonical storage and fast handle equality is useful.
• Embed structs.HostLayout in structures passed to or accessed by pointer from host APIs when host-compatible field layout is required.

Timers and runtime diagnostics

• Rely on unreachable timers and tickers being garbage-collected without calling Stop solely for reclamation.
• timer channels is unbuffered. After Timer.Stop or Timer.Reset, rely on the guarantee that stale values prepared earlier will not be delivered. Replace len(t.C) polling with a non-blocking receive.
• Available capability: GODEBUG=asynctimerchan=1 only as temporary migration support for code requiring the older buffered timer behaviour.
• runtime/debug.SetCrashOutput can direct fatal runtime reports to an automated crash collector.
• Available capability: runtime traces during crash investigation; Go 1.23 flushes trace data on uncaught panic and the trace tool recovers useful data from partially broken traces.

Standard library

• path/filepath.Localize can convert a valid slash-separated path safely to the operating system's path form.
• net.KeepAliveConfig is available when TCP keep-alive timing needs explicit control on dialled or accepted connections.
• Inspect cancellation and deadline causes from net.DNSError with errors.Is.
• Available capability: http.Request.CookiesNamed, http.ParseCookie, and http.ParseSetCookie when duplicate cookie names or strict parsing matter.
• Account for ServeContent, ServeFile, and ServeFileFS removing representation headers from error responses. Use GODEBUG=httpservecontentkeepheaders=1 only while migrating middleware that depended on the old behaviour.
• Available capability: reflect.Value.Seq or Seq2 only after Type.CanSeq or CanSeq2 when the dynamic type is not already known.
• sync.Map.Clear can empty a concurrent map rather than ranging and deleting entries individually.

TLS compatibility

• 3DES is absent from default cipher suites, while the experimental post-quantum X25519Kyber768Draft00 exchange is enabled by default. Config.CipherSuites and Config.CurvePreferences can express different interoperability requirements.
• tls.X509KeyPair and tls.LoadX509KeyPair populate Certificate.Leaf.
• Migration note: certificates using SHA-1 signatures; Go 1.24 removes the temporary verification escape hatch announced in this release.

Platform compatibility

• Platform requirement: macOS 11 or later.
• Compatibility outlook: Linux deployments for a minimum kernel of 3.2 before moving to Go 1.24.
• Configuration: GOARM64 when binaries require a specific minimum ARM64 architecture or the LSE or cryptographic extensions; otherwise retain the portable v8.0 default.