Go 1.24 (2025-02-11)

Go 1.24 was released in February 2025, six months after Go 1.23. Most changes are in the implementation of the toolchain, runtime, and libraries. Go 1.24 continues to uphold the Go 1 compatibility promise. Almost all Go programs are expected to continue to compile and run as before.

Language Changes

Go 1.24 now fully supports generic type aliases. Type aliases can be parameterized just like defined types. See the language specification for details. This feature can currently be disabled by setting GOEXPERIMENT=noaliastypeparams, but this setting will be removed in Go 1.25.

Toolchain

Go Command

• Tool Dependency Management: Go modules can now track executable dependencies using the tool directive in go.mod and run those tools using the go tool command. This eliminates the previous workaround of using "tools.go" files. See the documentation for more information.

  • Added the -tool flag to go get to add tool directives to the current module.
  • Added the tool meta-pattern to refer to all tools in the current module. You can use go get tool to upgrade all tools or go install tool to install them to the GOBIN directory.

• Cache Improvements: Executables created by go run and the new go tool behavior are now cached in the Go build cache, making repeated executions faster. See #69290.

• JSON Output:

  • The go build and go install commands now accept the -json flag to report build output and failures in structured JSON format. See go help buildjson for details.
  • go test -json now reports build output and failures in JSON format interleaved with test results. These are distinguished by a new Action type. To restore text build output, set the GODEBUG gotestjsonbuildtext=1.

• Private Module Authentication: Added the GOAUTH environment variable to provide a flexible way to authenticate private module fetches. See go help goauth for more information.

• Version Information: The go build command now sets the main module's version in the compiled binary based on version control system tags and/or commits. If there are uncommitted changes, a +dirty suffix is appended. Use the -buildvcs=false flag to omit version control information.

• Toolchain Tracing: Added the GODEBUG setting toolchaintrace=1 to trace the go command's toolchain selection process.

Cgo

Cgo supports new annotations to improve runtime performance:

• #cgo noescape cFunctionName: Tells the compiler that memory passed to the C function does not escape.
• #cgo nocallback cFunctionName: Tells the compiler that the C function does not call any Go functions.

See the cgo documentation for more information.

Cgo now better detects multiple incompatible declarations of C functions across files. For example, if f is declared as both void f(int) and void f(double), cgo reports an error instead of potentially generating incorrect call sequences for f(0). See #67699.

Objdump

The objdump tool now supports disassembly for the 64-bit LoongArch (GOARCH=loong64), RISC-V (GOARCH=riscv64), and S390X (GOARCH=s390x) architectures.

Vet

• New tests Analyzer: Reports common mistakes in tests, fuzz tests, benchmarks, and examples, such as misformatted names, incorrect signatures, or examples documenting non-existent identifiers. Some of these mistakes can cause tests not to run. This analyzer is part of the analyzers run by go test.

• printf Analyzer Improvements: Now reports calls like fmt.Printf(s) where s is a non-constant format string with no other arguments. Such calls are often mistakes because s may contain % symbols; fmt.Print should be used instead. See #60529. This check is only applied when the language version (as specified by the go directive in go.mod or //go:build comments) is at least Go 1.24 to avoid breaking CI when upgrading to the 1.24 toolchain.

• buildtag Analyzer Improvements: Reports diagnostics when invalid Go major version build constraints are present in //go:build directives. For example, //go:build go1.23.1 refers to a point release; //go:build go1.23 should be used instead. See #64127.

• copylock Analyzer Improvements: Reports diagnostics when variables declared in the three-clause "for" loop (e.g., for i := iter(); done(i); i = next(i) { ... }) contain sync.Locker (e.g., sync.Mutex). Go 1.22 changed the behavior of such loops to create a new variable for each iteration, copying the value from the previous iteration; this copying is unsafe for locks. See #66387.

GOCACHEPROG

The cmd/go internal binary and test caching mechanism can now be implemented by a subprocess named by the GOCACHEPROG environment variable, which implements a JSON protocol between the cmd/go tool and the subprocess. This previously required GOEXPERIMENT. See the documentation for protocol details.

Runtime

The runtime includes several performance improvements, reducing average CPU overhead by 2–3%, depending on the application. These improvements include:

• New Map Implementation: A new built-in map implementation based on Swiss Tables.
• Efficient Memory Allocation: More efficient memory allocation for small objects.
• New Mutex Implementation: A new runtime internal mutex implementation.

The new map implementation and new mutex implementation can be disabled by setting GOEXPERIMENT=noswissmap and GOEXPERIMENT=nospinbitmutex at build time, respectively.

References

For more details, please refer to the official release notes: Go 1.24 Release Notes