err := exec.Command("cp", "./test.go", "../test/test.go").Run()
if err != nil {
    println(err.Error())
}

$ go run main.go
exit status 1

// Exit causes the current program to exit with the given status code.
// Conventionally, code zero indicates success, non-zero an error.
// The program terminates immediately; deferred functions are not run.
//
// For portability, the status code should be in the range [0, 125].

// Exit 使當前程序停止運行，返回給定的狀態碼。
// 按照慣例，0表示成功，非0表示錯誤。
// 程序立即停止運行；之后的defer函數不再被運行。
//
// 為了可移植性，狀態碼的范圍應該是[0,125]。

package main

import (
  "os"
  "runtime"
)

func main() {
  recode := 0
  defer func() { os.Exit(recode) }()

  goos := runtime.GOOS
  if goos == "darwin" {
    recode = 2
    println("unsupported platform")
    return
  }
  println("success")
}