Repeat pipline

package main

import (
    "fmt"
)

func main() {
    repeat := func(
        done <-chan interface{},
        values ...interface{},
    ) <-chan interface{} {
        valueStream := make(chan interface{})
        go func() {
            defer close(valueStream)
            for {
                for _, v := range values {
                    select {
                    case <-done:
                        return
                    case valueStream <- v:
                    }
                }
            }
        }()
        return valueStream
    }

    take := func(
        done <-chan interface{},
        valueStream <-chan interface{},
        num int,
    ) <-chan interface{} {
        takeStream := make(chan interface{})
        go func() {
            defer close(takeStream)
            for i := 0; i < num; i++ {
                select {
                case <-done:
                    return
                case takeStream <- <-valueStream:
                }
            }
        }()
        return takeStream

    }

    done := make(chan interface{})
    defer close(done)

    for num := range take(done, repeat(done, 1, 2, 3, 4), 10) {
        fmt.Printf("%v ", num)
    }

    fmt.Println()

}

程序输出如下，

image.png