Go 1.8 (2017-02-16)

Go 1.8 was released on February 16, 2017. This release maintains the Go 1 compatibility promise while bringing significant performance improvements (especially GC and defer), as well as important features like HTTP/2 Server Push, HTTP Server graceful shutdown, and a plugin system.

Major Changes

Language

• Struct Conversion Ignoring Tags: When explicitly converting one struct type to another, if they differ only in field tags, the conversion is now allowed directly without requiring field tags to match exactly.

  type T1 struct {
      X int `json:"foo"`
  }
  type T2 struct {
      X int `json:"bar"`
  }
  var v1 T1
  var v2 T2
  v1 = T1(v2) // Illegal before Go 1.8, now legal

Toolchain

• Plugin System: Go 1.8 introduced preliminary support for dynamically loading shared libraries (currently Linux only). The plugin package allows Go programs to load Go packages compiled as plugins (.so files) at runtime and look up exported symbols (variables or functions).

  p, err := plugin.Open("myplugin.so")
  f, err := p.Lookup("MyFunction")

• Default GOPATH: If the GOPATH environment variable is not set, Go now uses a default value:

  • Unix: $HOME/go
  • Windows: %USERPROFILE%\go

Runtime

• Garbage Collection (GC): GC pause times are further reduced, typically under 100 microseconds, and even as low as 10 microseconds. This is due to the elimination of "stop-the-world" stack rescanning.
• Defer Overhead: The overhead of defer function calls is reduced by about half.
• Cgo Overhead: The overhead of calling C code from Go is also reduced by about half.
• mutex Profiling: Support for profiling mutex contention (go test -mutexprofile).

Standard Library

• HTTP/2 Server Push: The net/http package added support for HTTP/2 Server Push. This allows the server to push resources before the client requests them. http.ResponseWriter now implements the Pusher interface.

  if pusher, ok := w.(http.Pusher); ok {
      // Push is supported.
      if err := pusher.Push("/style.css", nil); err != nil {
          log.Printf("Failed to push: %v", err)
      }
  }

• HTTP Server Graceful Shutdown: http.Server added the Shutdown method, supporting graceful server shutdown. Shutdown stops listening for new requests but allows currently processing requests to complete before closing the server.

  ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
  defer cancel()
  if err := srv.Shutdown(ctx); err != nil {
      log.Fatal("Server Shutdown:", err)
  }

• sort.Slice: The sort package added the Slice function, making it much simpler to sort slices without defining a new type to implement sort.Interface.

  sort.Slice(people, func(i, j int) bool {
      return people[i].Name < people[j].Name
  })

• Context Support Extension: Support for context.Context has been extended to more standard libraries:

  • database/sql: Added QueryContext, ExecContext, PrepareContext, etc., allowing database operations to be cancelled via Context.
  • net.Resolver: DNS query methods now accept Context.

• encoding/base64: Added Strict mode to strictly check padding bits.

• encoding/json: Marshal now supports floating-point number formatting consistent with ES6.

References

For more details, please refer to the official release notes: Go 1.8 Release Notes