Go 1 22

Go 1.22

This overview applies when the project's target Go version is at least 1.22.

Language

• Loop variables declared by a for loop are distinct for every iteration, making defensive shadow assignments for closures and goroutines unnecessary.
• Integer ranges iterate from zero to one less than a bound.

for index := range count {
	process(index)
}

• GOEXPERIMENT=rangefunc enables a preview of range-over-function iterators; it is not a stable Go 1.22 language feature.

Tools and workspaces

• go work vendor creates a shared vendor directory for a multi-module workspace; that directory cannot simultaneously represent single-module vendoring state.
• go get no longer works in legacy GOPATH mode, so dependency changes occur inside modules.
• go test -cover reports zero coverage for packages containing executable code but no tests.
• go vet detects ineffective append calls, prematurely evaluated time.Since calls in defer, and malformed alternating key-value arguments to log/slog.
• The refreshed execution tracer supports streamable traces, complete system-call durations, and correlation with operating-system clocks. GOEXPERIMENT=noexectracer2 restores the older tracer temporarily.

Randomness and versions

• math/rand/v2 is the modern non-cryptographic random-number API, with IntN, UintN, generic N, and the PCG and ChaCha8 sources for local state.
• crypto/rand.Read remains the API for random bytes that protect secrets; math/rand/v2 is not a substitute.
• go/version validates and compares Go version strings without ad hoc parsing.

HTTP routing and filesystems

• http.ServeMux patterns can include HTTP methods and wildcards, with wildcard values available through Request.PathValue.

mux.HandleFunc("GET /items/{id}", func(writer http.ResponseWriter, request *http.Request) {
	id := request.PathValue("id")
	serveItem(writer, request, id)
})

• Braces, escaped paths, and conflicting patterns can behave differently under the new routing semantics; GODEBUG=httpmuxgo121=1 temporarily restores the old behaviour.
• http.ServeFileFS, http.FileServerFS, and http.NewFileTransportFS serve content from an fs.FS.
• archive/tar.Writer.AddFS and archive/zip.Writer.AddFS add an fs.FS without a manual walk.

Standard library and runtime

• cmp.Or selects the first non-zero value in an ordered fallback sequence.
• slices.Concat concatenates multiple slices. Delete, DeleteFunc, Compact, CompactFunc, and Replace now zero obsolete elements.
• reflect.TypeFor[T]() replaces the reflect.TypeOf((*T)(nil)).Elem() idiom, and reflect.PointerTo replaces deprecated reflect.PtrTo.
• /sched/pauses/total/gc:seconds replaces the deprecated /gc/pauses:seconds metric, with additional histograms separating stop coordination from complete pauses.
• go/types can expose alias nodes under GODEBUG=gotypesalias=1, so named-looking types are not necessarily *types.Named.

Security and compatibility

• TLS servers with no explicit minimum require TLS 1.2, and pre-TLS 1.3 defaults exclude non-ECDHE cipher suites. tls10server=1 and tlsrsakex=1 provide temporary legacy compatibility.
• CertPool.AddCertWithConstraint associates additional chain-building checks with a custom trust root.
• slices.Insert panics for every out-of-range insertion index, including when no values are inserted.