图0:让Go无路可go的十个方法

本节有且仅有一个目的,那就是让Go程序遇到“panic”。

1.数组/切片索引越界

func main() {
	names := []string{
		"煎鱼",
		"eddycjy",
		"Go编程之旅",
	}
	name := names[len(names)]
	fmt.Printf("name: %s", name)
}

运行结果:

panic: runtime error: index out of range [3] with length 3
goroutine 1 [running]:
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:11 +0x1b

2. 空指针调用

type User struct {
	Name string
}
func (u *User) GetName() string {
	return u.Name
}
func main() {
	s := &User{Name: "煎鱼"}
	s = nil
	s.GetName()
}

运行结果:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x1056f62]
goroutine 1 [running]:
main.(*User).GetName(...)
        /Users/eddycjy/go-application/awesomePanic/main.go:8
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:14 +0x2

3.过早关闭HTTP响应体

func main() {
	resp, err := http.Get("https://xxx")
	defer resp.Body.Close()
	if err != nil {
		log.Fatalf("http.Get err: %v", err)
	}
}

运行结果:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x123d4d3]
goroutine 1 [running]:
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:10 +0x63

4.除以零

func divide(a, b int) int {
	return a / b
}
func main() {
	divide(1, 0)
}

运行结果:

panic: runtime error: integer divide by zero
goroutine 1 [running]:
main.divide(...)
        /Users/eddycjy/go-application/awesomePanic/main.go:4
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:8 +0x12

5.向已关闭的通道发送消息

func main() {
	ch := make(chan string, 1)
	ch <- "煎鱼"
	close(ch)
	ch <- "Go编程之旅"
}

运行结果:

panic: send on closed channel
goroutine 1 [running]:
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:7 +0x7d

6.重复关闭通道

func main() {
	ch := make(chan string, 1)
	ch <- "Go编程之旅"
	close(ch)
	close(ch)
}

运行结果:

panic: close of closed channel
goroutine 1 [running]:
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:7 +0x71

7. 关闭未初始化的通道

func main() {
	var ch chan string
	close(ch)
}

运行结果:

panic: close of nil channel
goroutine 1 [running]:
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:5 +0x2a

8.未初始化map

func main() {
	var m map[string]string
	m["Go编程之旅"] = "一起用Go做项目"
}

运行结果:

panic: assignment to entry in nil map
goroutine 1 [running]:
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:5 +0x4b

9.跨协程的“恐慌”处理

func main() {
	go func() {
		defer func() {
			if err := recover(); err != nil {
				log.Fatalf("recover err: %v", err)
			}
		}()
		handle()
	}()
	time.Sleep(time.Second)
}
func handle() {
	go divide(1, 0)
}
func divide(a, b int) int {
	return a / b
}

运行结果:

panic: runtime error: integer divide by zero
goroutine 17 [running]:
main.divide(0x1, 0x0, 0x0)
        /Users/eddycjy/go-application/awesomePanic/main.go:34 +0x40
created by main.handle
        /Users/eddycjy/go-application/awesomePanic/main.go:30 +0x47

10. sync计数为负值

func main() {
	wg := sync.WaitGroup{}
	wg.Add(-1)
	wg.Wait()
}

运行结果:

panic: sync: negative WaitGroup counter
goroutine 1 [running]:
sync.(*WaitGroup).Add(0xc000104000, 0xffffffffffffffff)
        /usr/local/Cellar/go/1.14/libexec/src/sync/waitgroup.go:74 +0x139
main.main()
        /Users/eddycjy/go-application/awesomePanic/main.go:7 +0x44

本文节选自《Go语言编程之旅:一起用Go做项目》

陈剑煜徐新华 著

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