上面的代码有点误人子弟, 进程结束了, 还有 goroutine 没跑完. 还是改一下.

```

package main

import (
"fmt"
"sync"
"time"
)


var (
count = 10
ch = make(chan int, count)
)

func main() {

wg := sync.WaitGroup{}

for i := 0; i < count * 3; i ++ {

ch <- i
wg.Add(1)

go test(i, &wg)
}


wg.Wait()
}

func test(i int, wg *sync.WaitGroup) {

// TODO
fmt.Printf("run task %d\n", i)
time.Sleep(time.Second * 3)

<- ch
wg.Done()
}

```

http://www.dooccn.com/go/#id/6e2ac7e2e4c73ce14fef393c93d4c80f