使用recover恢复panic

package main

import (  
    "fmt"
)

func r() {  
    if r := recover(); r != nil {
        fmt.Println("Recovered", r)
        //debug.PrintStack()
    }
}

func a() {  
    defer r()
    n := []int{5, 7, 4}
    fmt.Println(n[3])
    fmt.Println("normally returned from a")
}

func main() {  
    a()
    fmt.Println("normally returned from main")
}