golang中channel的用法

go语言的range循环可以直接在channels上面迭代。使用range循环一次从channel中接受数据，当channel被关闭并且没有值可接受时跳出循坏。

func main() {
    natures := make(chan int)
    squares := make(chan int)

    go func() {
        for x := 0; x < 100; x++ {
            natures <- x
        }
        close(natures)
    }()

    go func() {
        for x := range natures {
            squares <- x * x
        }

        close(squares)
    }()

    for x := range squares {
        fmt.Println(x)
    }
}

双向channel可以隐式转换为单向channel，反之不行

func main() {
    natures := make(chan int)
    squares := make(chan int)
    go counter(natures)
    go squar(natures,squares)
    printer(squares)
}

func squar(in <-chan int,out chan<- int) {
    for i:= range in {
        out <- i*i
    }
    close(out)
}
func printer(in <-chan int) {
    for i := range in {
        fmt.Println(i)
    }
}

func counter(out chan<- int) {
    for i:=0;i<100;i++ {
        out <- i
    }
    close(out)
}

多个goroutines并发地向同一个channel发送数据，返回最快响应的，此时应该采用有缓冲的channel，否则，其他goroutine返回之后没有通道接受，则产生goroutine卡死，泄露

func mirroredQuery() string {
    responses := make(chan string, 3)
    go func() { responses <- request("asia.gopl.io") }()
    go func() { responses <- request("europe.gopl.io") }()
    go func() { responses <- request("americas.gopl.io") }()
    return <-responses // return the quickest response
}