附录 D：让 Go panic 的十种方法
本章节有且仅有一个目的，那就是让你的 Go 程序遇到 panic。
D.1 数组/切片索引越界
func main() {
names := []string{
"煎鱼",
"eddycjy",
"Go 语言编程之旅",
}
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
D.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
D.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
D.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
D.5 向已关闭的通道发消息
func main() {
ch := make(chan string, 1)
ch <- "煎鱼"
close(ch)
ch <- "Go 语言编程之旅"
}
运行结果：
panic: send on closed channel
goroutine 1 [running]:
main.main()
/Users/eddycjy/go-application/awesomePanic/main.go:7 +0x7d
D.6 重复关闭通道
func main() {
ch := make(chan string, 1)
ch <- "Go 语言编程之旅"
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
D.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
D.8 未初始化 map
func main() {
var m map[string]string
m["Go 语言编程之旅"] = "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
D.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
D.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
