switch i {
	case 0: // 空分支，只有当 i == 0 时才会进入分支
	case 1:
		f() // 当 i == 0 时函数不会被调用
}

switch i {
	case 0: fallthrough
	case 1:
		f() // 当 i == 0 时函数也会被调用
}

k := 6
switch k {
	case 4: fmt.Println("was <= 4"); fallthrough;
	case 5: fmt.Println("was <= 5"); fallthrough;
	case 6: fmt.Println("was <= 6"); fallthrough;
	case 7: fmt.Println("was <= 7"); fallthrough;
	case 8: fmt.Println("was <= 8"); fallthrough;
	default: fmt.Println("default case")
}