戈朗通道缺少一些值

Question

我有以下代码package mainimport (    "fmt"    "math/rand"    "time")func main() {    concurrent := 12    ch := make(chan int)    defer close(ch)    for i := 1; i <= concurrent; i++ {        go worker(i, ch)    }    for i := 1; i <= 21; i++ {        ch <- i    }}func worker(worker int, ch chan int) {    for requestId := range ch {        fmt.Printf("worker %d is requesting to %d...\n", worker, requestId)        time.Sleep(time.Duration(rand.Intn(3)) * time.Second)    }}该函数启动运行该函数的多个 goroutine，然后将一些值放入通道中，这些值由 worker 打印。我的问题是，有时通道中的最后一个值甚至更多值不是由工作人员打印的。mainworkerworker 10 is requesting to 10...worker 5 is requesting to 1...worker 5 is requesting to 13...worker 7 is requesting to 6...worker 2 is requesting to 2...worker 3 is requesting to 7...worker 3 is requesting to 14...worker 6 is requesting to 4...worker 11 is requesting to 9...worker 9 is requesting to 8...worker 9 is requesting to 15...worker 12 is requesting to 11...worker 8 is requesting to 12...worker 8 is requesting to 16...worker 4 is requesting to 5...worker 1 is requesting to 3...worker 11 is requesting to 17...我认为这是因为主要功能在打印最后一个值之前结束并“杀死”所有运行goroutine，因为最后所有值都始终被打印出来。func main() {    concurrent := 12    ch := make(chan int)    defer close(ch)    for i := 1; i <= concurrent; i++ {        go worker(i, ch)    }    for i := 1; i <= 21; i++ {        ch <- i    }    time.Sleep(3 * time.Second)}如何在不使用睡眠的情况下解决此问题，并且如果可能的话仅使用通道？

Answer 1

因为主 goroutine 在最后一个循环之后立即退出，导致整个程序也退出，所以后台 goroutines 可能会也可能不会有机会运行，你必须提供一些同步方法来“等待”所有工作线程完成。for

用sync.WaitGroup

   func main() {

    concurrent := 12

    ch := make(chan int)

    var wg sync.WaitGroup

    for i := 1; i <= concurrent; i++ {

        wg.Add(1)

        go func(i int) {

            defer wg.Done()

            worker(i, ch)

        }(i) // You have to pass i as parameter

    }

    for i := 1; i <= 21; i++ {

        ch <- i

    }

    close(ch) // Close channel to tell all workers to stop

    wg.Wait() // Wait all workers to finish its work

   }