讓Go無路可go的十個方法
本節有且僅有一個目的,那就是讓Go程序遇到“panic”。
1.數組/切片索引越界
func main() { names := []string{ "煎魚", "eddycjy", "Go編程之旅", } name := names[len(names)] fmt.Printf("name: %s", name) }
運行結果:
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. 空指針調用
type User struct { Name string } func (u *User) GetName() string { return u.Name } func main() { s := &User{Name: "煎魚"} s = nil s.GetName() }
運行結果:
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.過早關閉HTTP響應體
func main() { resp, err := http.Get("https://xxx") defer resp.Body.Close() if err != nil { log.Fatalf("http.Get err: %v", err) } }
運行結果:
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) }
運行結果:
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.向已關閉的通道發送消息
func main() { ch := make(chan string, 1) ch <- "煎魚" close(ch) ch <- "Go編程之旅" }
運行結果:
panic: send on closed channel goroutine 1 [running]: main.main() /Users/eddycjy/go-application/awesomePanic/main.go:7 +0x7d
6.重複關閉通道
func main() { ch := make(chan string, 1) ch <- "Go編程之旅" close(ch) close(ch) }
運行結果:
panic: close of closed channel goroutine 1 [running]: main.main() /Users/eddycjy/go-application/awesomePanic/main.go:7 +0x71
7. 關閉未初始化的通道
func main() { var ch chan string close(ch) }
運行結果:
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編程之旅"] = "一起用Go做項目" }
運行結果:
panic: assignment to entry in nil map goroutine 1 [running]: main.main() /Users/eddycjy/go-application/awesomePanic/main.go:5 +0x4b
9.跨協程的“恐慌”處理
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 }
運行結果:
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計數爲負值
func main() { wg := sync.WaitGroup{} wg.Add(-1) wg.Wait() }
運行結果:
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
本文節選自 《Go語言編程之旅:一起用Go做項目》
陳劍煜徐新華 著