go - 为什么会有这样的结果？

Question

我编写了一个golang脚本来扫描打开的端口并使用sync.WaitGourp来控制goroutine的数量。
当goroutine太大(例如2000)时，结果不同于1000。
类似于提前退出。代码显示如下

func worker(wg *sync.WaitGroup) {
    for job := range jobs {
        _, err := net.DialTimeout("tcp", fmt.Sprintf("%s:%d", job.host, job.port), time.Millisecond*1500)
        if err != nil {
            results <- Result{job, false}
        } else {
            results <- Result{job, true}
        }
    }
    wg.Done()
}

func main() {
    go func() {
        for i := 1; i < 65535; i++ {
            jobs <- Job{host, i}
        }
        close(jobs)
    }()

    go func() {
        for result := range results {
            if result.status {
                fmt.Println(result.job, "open")
            }
        }
    }()

    wg := sync.WaitGroup{}
    for i := 1; i < 1000; i++ {
        wg.Add(1)
        go worker(&wg)
    }
    wg.Wait()
}

当1000

{127.0.0.1 80} open{127.0.0.1 631} open{127.0.0.1 3306} open{127.0.0.1 6379} open{127.0.0.1 33060} open

当2000

{127.0.0.1 80} open{127.0.0.1 631} open

我希望2000输出所有端口，例如1000

Answer 1

工作人员完成后，关闭结果 channel 。在主goroutine中处理结果。

wg := sync.WaitGroup{}
for i := 1; i < 1000; i++ {
    wg.Add(1)
    go worker(&wg)
}

go func() {
    for i := 1; i < 65535; i++ {
        jobs <- Job{host, i}
    }

    // No more jobs, exit from worker loops.
    close(jobs)

    // Wait for workers to write all results and exit.
    wg.Wait()

    // No more results, exit from main loop.
    close(results)

}()

for result := range results {
    if result.status {
        fmt.Println(result.job, "open")
    }
}

View the complete program on the GoLang PlayGround。