Go 1.16 (2021-02-16)

Go 1.16 was released in February 2021, introducing file embedding (embed) support and enabling Go Modules by default.

Major Changes

Toolchain

• Go Modules Enabled by Default: The default value of the GO111MODULE environment variable is now on. The Go command now runs in Module mode by default, regardless of whether the current directory contains a go.mod file.

  • The go install command now supports the pkg@version syntax for installing executables of a specific version without affecting the dependencies of the current project. For example: go install golang.org/x/tools/gopls@latest.
  • go build and go test no longer automatically modify go.mod and go.sum. If dependencies need to be updated, go mod tidy or go get must be run explicitly.

• Embedding Static Files (Embed): Introduced the //go:embed directive, allowing static files (such as HTML, CSS, images, etc.) to be directly embedded into the compiled Go binary.

  package main
  
  import (
      "embed"
      "fmt"
  )
  
  //go:embed hello.txt
  var f embed.FS
  
  func main() {
      data, _ := f.ReadFile("hello.txt")
      fmt.Print(string(data))
  }

• Linker Optimization: Linker speed improved by 20-25%, and memory usage reduced by 5-15%.

• go build -overlay: Supports the -overlay flag, mainly for editor tools (such as gopls).

• go vet: Added checks for incorrect use of testing.T in goroutines.

Runtime

• Apple Silicon (M1) Support: Added darwin/arm64 port, officially supporting running Go programs natively on Macs with Apple Silicon (M1) chips.
• runtime/metrics: Added a new package providing a more stable and general interface for reading runtime metrics.
• GODEBUG=inittrace=1: Setting this environment variable traces the execution time and memory allocation of init functions, helping to analyze startup performance.
• Linux Memory Release: On Linux, the runtime now defaults to using MADV_DONTNEED to quickly release memory to the operating system, instead of MADV_FREE.

Standard Library

• io/fs: Introduced the fs.FS interface, defining an abstraction for read-only file systems. Many packages in the standard library (such as net/http, html/template) have been adapted to this interface.
• embed: Added the embed standard library package, providing methods to access embedded files.
• io/ioutil Deprecation: The io/ioutil package is marked as deprecated (although still usable, migration is recommended). Its functionality has been moved to the io and os packages:
  • ioutil.Discard -> io.Discard
  • ioutil.NopCloser -> io.NopCloser
  • ioutil.ReadAll -> io.ReadAll
  • ioutil.ReadDir -> os.ReadDir (returns os.DirEntry slice)
  • ioutil.ReadFile -> os.ReadFile
  • ioutil.WriteFile -> os.WriteFile
  • ioutil.TempDir -> os.MkdirTemp
  • ioutil.TempFile -> os.CreateTemp
• os/signal: Added NotifyContext function, creating a Context that is canceled when a signal is received.
• path/filepath: Added WalkDir function, which is more efficient than Walk (avoids calling os.Lstat for every file).
• net/http: Adjusted default behavior for SameSite cookie attribute.
• strconv: ParseFloat uses the faster Eisel-Lemire algorithm.

References

For more details, please refer to the official release notes: Go 1.16 Release Notes