fallthrough：Go里面switch默认相当于每个case最后带有break，匹配成功后不会自动向下执行其他case，而是跳出整个switch, 但是可以使用fallthrough强制执行后面的case代码。
示例程序1：
switch {
case false:
fmt.Println("The integer was <= 4")
fallthrough
case true:
fmt.Println("The integer was <= 5")
fallthrough
case false:
fmt.Println("The integer was <= 6")
fallthrough
case true:
fmt.Println("The integer was <= 7")
fallthrough
case false:
fmt.Println("The integer was <= 8")
default:
fmt.Println("default case")
}
输出结果：
The integer was <= 5
The integer was <= 6
The integer was <= 7
The integer was <= 8
问题：是否在switch最后一个分支使用fallthrough？？？
有错误提示，显示：cannot fallthrough final case in switch
fallthrough不能用在switch的最后一个分支。
示例程序2：
上述示例是true、false常量进行分支判断，看如下变量示例。
s := "abcd"
switch s[1] {
case 'a':
fmt.Println("The integer was <= 4")
fallthrough
case 'b':
fmt.Println("The integer was <= 5")
fallthrough
case 'c':
fmt.Println("The integer was <= 6")
default:
fmt.Println("default case")
}
输出结果如下：
The integer was <= 5
The integer was <= 6
更改为：
s := "abcd"
switch s[3] {
case 'a':
fmt.Println("The integer was <= 4")
fallthrough
case 'b':
fmt.Println("The integer was <= 5")
fallthrough
case 'c':
fmt.Println("The integer was <= 6")
default:
fmt.Println("default case")
}
输出：
default case
总结：switch分支中使用变量进行判断的时，fallthrough正确的分支开始其作用。