package main

import "fmt"

func main() {
    is := []int{1, 2}

    fmt.Println(is[2:]) // no panic here - this includes is[2] which is out of bound still no panic
    fmt.Println(is[3:]) // but panic here
    fmt.Println(is[2]) // panic here which is acceptable
}

在上面提到的程序中，即使我们正在从is [2]到on病房访问元素，并且片中只有2个元素，也没有为is [2：]感到恐慌。为什么会这样呢？