Go language previews performance-boosting garbage collector

Go 1.25, the latest version of the Google-developed open source programming language, has been released. The update brings new capabilities including an experimental garbage collector that improves performance, a fix for a compiler bug that could delay pointer checks, and a package that provides support for testing concurrent code.

Announced August 12 by the Go team, Go 1.25 can be accessed at go.dev. The release includes enhancements across tools, the runtime, the standard library, the compiler, and the linker.

The new garbage collector has a design that improves performance of marking and scanning small objects through better locality and CPU scalability, according to the Go team. The team expects a 10% to 40% reduction in garbage collection overhead in real-world programs that heavily use the collector. Developers can enable the collector by setting GOEXPERIMENT=greenteaqc at build time. 

For the compiler, meanwhile, the release fixes a bug from Go 1.21 that could incorrectly delay nil pointer checks. Programs like the one below, which used to execute successfully when they shouldn’t, the Go team said, 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)
}

In the standard library, Go 1.25 has a new testing/synctest  package that supports testing for concurrent code. The Test function runs a test function in an isolated “bubble,” the team said. 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. Also, the Wait function waits for all goroutines in the current bubble to block. This package first became available in Go 1.24 under GOEXPERIMENT=synctest, with a slightly different API. The experiment has graduated to general availability.

Go 1.25 follows Go 1.24, which was introduced in February with enhancements pertaining to generic type aliases and WebAssembly. The Go language has gained attention lately with Microsoft’s plan to port the TypeScript compiler and tools to the language, with the intent of boosting performance.

Also featured in Go 1.25:

An experimental JSON implementation, when enabled, provides an encoding/json/v2 package, which is a major revision of the encoding/json package, and the encoding/json/jsontext package, which provides lower-level processing of JSON syntax.

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 Go or C.

The compiler now can allocate the backing store for slices on the stack in more situations, improving performance.

The compiler and linker now generate debug information using DWARF (debugging with attributed record formats) Version 5.

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

The linker now accepts a -funcalign=N command line option that specifies the alignment of function entries. The default value is platform-dependent and unchanged in Go 1.25.

For cryptography, MessageSigner is a signing interface that can be implemented by signers that wish to hash the message to be signed themselves.