如何从多个goroutine写入同一通道

Question

I need several goroutines to write in the same channel. Then all the data is read in one place until all the goroutines complete the process. But I'm not sure how best to close this channel.

this is my example implementation:

func main() {
    ch := make(chan data)
    wg := &sync.WaitGroup{}
    for instance := range dataSet {
        wg.Add(1)
        go doStuff(ch, instance)
    }
    go func() {
        wg.Wait()
        close(ch)
    }()

    for v := range ch { //range until it closes
        //proceed v
    }
}

func doStuff(ch chan data, instance data) {
    //do some stuff with instance...
    ch <- instance
}

but I'm not sure that it is idiomatic.

Answer 1

As you are using WaitGroup and increase the counter at the time of starting new goroutine, you have to notify WaitGroup when a goroutine is finished by calling the Done() method. Also you have to pass the same WaitGroup to the goroutine. You can do it by passing the address of WaitGroup. Otherwise each goroutine will use it's own WaitGroup which will be on different scope.

func main() {
    ch := make(chan data)
    wg := &sync.WaitGroup{}
    for _, instance := range dataSet {
        wg.Add(1)
        go doStuff(ch, instance, wg)
    }
    go func() {
        wg.Wait()
        close(ch)
    }()

    for v := range ch { //range until it closes
        //proceed v
    }
}

func doStuff(ch chan data, instance data, wg *sync.WaitGroup) {
    //do some stuff with instance...
    ch <- instance

    // call done method to decrease the counter of WaitGroup
    wg.Done()
}