for select switch遍历channel

之前在做测试的时候，写过这样一个协程的例子，运行之后发现Recive函数一直没有退出

func main() {
  flag :=  make(chan int,1)
    msg := make(chan interface{},100)

    go Send(msg)
    go Recive(msg)
    <-flag
}
func Send(msgChan chan interface{})  {
    msgChan<-Msg{Name:"test"}
    msgChan<-"close"
}

func Recive(msgChan chan interface{})  {
    for {
        select {
        case msg := <-msgChan:
            switch msg.(type) {
            case Msg:
                log.Println("type Msg",msg)
            case string:
                log.Println("type string",msg)
                if msg=="close" {
                    close(msgChan)
                    break
                }
            }
        default:
            log.Println("select")
        }
        log.Println("for")
    }
}

运行结果如下：

2019/09/12 22:08:46 type Msg {test}
2019/09/12 22:08:47 for
2019/09/12 22:08:47 type string close
2019/09/12 22:08:48 for
2019/09/12 22:08:49 for
2019/09/12 22:08:50 for
......
2019/09/12 22:10:28 for

发现Recive在接收到close的消息之后进行了break，但是只是break出了select的代码块，for循环依然在运行，因此直接break是无法跳出for循环，需要使用break 标签这种方式来中断

func Recive(msgChan chan interface{})  {
    L:
    for {
        select {
        case msg := <-msgChan:
            switch msg.(type) {
            case Msg:
                log.Println("type Msg",msg)
            case string:
                log.Println("type string",msg)
                if msg=="close" {
                    close(msgChan)
                    break L
                }
            }
        default:
            time.Sleep(time.Second)
            log.Println("select")
        }
        time.Sleep(time.Second)
        log.Println("for")
    }
}