package main

import (
 "fmt"
)

func main() {
 fmt.Println("a return:", a()) // 打印结果为 a return: 0
}

func a() int {
 var i int
 defer func() {
  i++
  fmt.Println("a defer2:", i) // 打印结果为 a defer2: 2
 }()
 defer func() {
  i++
  fmt.Println("a defer1:", i) // 打印结果为 a defer1: 1
 }()
 return i
}

package main

import (
 "fmt"
)

func main() {
 fmt.Println("b return:", b()) // 打印结果为 b return: 2
}

func b() (i int) {
 defer func() {
  i++
  fmt.Println("b defer2:", i) // 打印结果为 b defer2: 2
 }()
 defer func() {
  i++
  fmt.Println("b defer1:", i) // 打印结果为 b defer1: 1
 }()
 return i // 或者直接 return 效果相同
}

package main

import (
 "fmt"
)

func main() {
 c:=c()
 fmt.Println("c return:", *c, c) // 打印结果为 c return: 2 0xc082008340
}

func c() *int {
 var i int
 defer func() {
  i++
  fmt.Println("c defer2:", i, &i) // 打印结果为 c defer2: 2 0xc082008340
 }()
 defer func() {
  i++
  fmt.Println("c defer1:", i, &i) // 打印结果为 c defer1: 1 0xc082008340
 }()
 return &i
}

package main

import (
 "fmt"
 "time"
)

func main() {
 defer P(time.Now())
 time.Sleep(5e9)
 fmt.Println("main ", time.Now())
}

func P(t time.Time) {
 fmt.Println("defer", t)
 fmt.Println("P ", time.Now())
}

// 输出结果：
// main 2017-08-01 14:59:47.547597041 +0800 CST
// defer 2017-08-01 14:59:42.545136374 +0800 CST
// P  2017-08-01 14:59:47.548833586 +0800 CST

package main

import (
 "errors"
 "fmt"
 "time"
 // "os"
)

func main() {
 e := errors.New("error")
 fmt.Println(e)
 // （3）panic(e) // defer 不会执行
 // （4）os.Exit(1) // defer 不会执行
 defer fmt.Println("defer")
 // （1）go func() { panic(e) }() // 会导致 defer 不会执行
 // （2）panic(e) // defer 会执行
 time.Sleep(1e9)
 fmt.Println("over.")
 // （5）os.Exit(1) // defer 不会执行
}

package main

import (
 "fmt"
)

func main() {
 defer fmt.Print(1)
 defer fmt.Print(2)
 defer fmt.Print(3)
 defer fmt.Print(4)
}