func job(i int) {
    fmt.Println(i)
    time.Sleep(time.Second)
}

func main() {
    maxNum := 10

    pool := make(chan struct{}, maxNum) // 协程池

    wg := sync.WaitGroup{}
    for i := 0; i < 100; i++ {
        pool <- struct{}{}
        wg.Add(1)
        go func(i int) {
            defer wg.Done()
            defer func() {
                <-pool
            }()

            job(i)
        }(i)
    }

}