if condition {
    分支1
} else if condition {
    分支2
} else {
    分支3
}

for 初始语句;条件表达式;结束语句 {
    循环体语句
}

for i := 0; i < 10; i++ {
	fmt.Println(i)
}

for != nil {
    ...
}

for {
    ...
}

//遍历切片
s := []int{1, 2, 3, 4, 5}
for k, v := range s {
    fmt.Println(k, v)
}

//遍历map
m := make(map[string]int)
m["key1"] = 1
m["key2"] = 2
m["key3"] = 3
for k, v := range m {
    fmt.Println(k, v)
}

n := 2
switch n {
case 1:
    fmt.Println("case 1 hit!")
case 2:
    fmt.Println("case 2 hit!")
default:
    fmt.Println("no case hit!")
}