学一手Golang的recover使用

关于Golang中的 recover

环境：

Go v1.12.7
MacOS 10.15
iris v11.1.1

今天看 iris 源码时看到了它的recover中间件的写法，感觉写的不错，摘录如下

// New returns a new recover middleware,
// it recovers from panics and logs
// the panic message to the application's logger "Warn" level.
func New() context.Handler {
  return func(ctx context.Context) {
    defer func() {
      if err := recover(); err != nil {
        if ctx.IsStopped() {
          return
        }

        var stacktrace string
        for i := 1; ; i++ {
          _, f, l, got := runtime.Caller(i)
          if !got {
            break
          }

          stacktrace += fmt.Sprintf("%s:%d\n", f, l)
        }

        // when stack finishes
        logMessage := fmt.Sprintf("Recovered from a route's Handler('%s')\n", ctx.HandlerName())
        logMessage += fmt.Sprintf("At Request: %s\n", getRequestLogs(ctx))
        logMessage += fmt.Sprintf("Trace: %s\n", err)
        logMessage += fmt.Sprintf("\n%s", stacktrace)
        ctx.Application().Logger().Warn(logMessage)

        ctx.StatusCode(500)
        ctx.StopExecution()
      }
    }()

    ctx.Next()
  }
}

不但使用了 recover 防止程序因为 panic 而退出，而且使用了 runtime.Caller() 打印出错堆栈信息。

我自己写了一个demo，如下

package main

import (
    "fmt"
    "log"
    "runtime"
)

func func3() {
    panic("something error in func3")
}

func func2() {
    func3()
}

func func1() {
    func2()
}

func main() {
    defer func() {
       if err := recover(); err != nil {
           var stacktrace string
           for i := 1; ; i++ {
               _, f, l, got := runtime.Caller(i)
               if !got {
                   break
               }
               stacktrace += fmt.Sprintf("%s:%d\n", f, l)
           }
           log.Printf("panic: %v\n" + stacktrace, err)
       }
    }()
    func1()
}

执行后打印结果如下，prefect！

[I] > go run app.go
2019/10/19 19:58:59 panic: something error in func3
/usr/local/Cellar/go/1.12.7/libexec/src/runtime/panic.go:522
/Users/nizhenyang/my-project/algorithm/leetcode/playground/play/recover/app.go:10
/Users/nizhenyang/my-project/algorithm/leetcode/playground/play/recover/app.go:14
/Users/nizhenyang/my-project/algorithm/leetcode/playground/play/recover/app.go:18
/Users/nizhenyang/my-project/algorithm/leetcode/playground/play/recover/app.go:35
/usr/local/Cellar/go/1.12.7/libexec/src/runtime/proc.go:200
/usr/local/Cellar/go/1.12.7/libexec/src/runtime/asm_amd64.s:1337

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