Always have x number of goroutines running at any time

Question

I see lots of tutorials and examples on how to make Go wait for x number of goroutines to finish, but what I\'m trying to do is have ensure there are always x number running

Answer 1

Grzegorz Żur's answer is the most efficient way to do it, but for a newcomer it could be hard to implement without reading code, so here's a very simple implementation:

type idProcessor func(id uint)

func SpawnStuff(limit uint, proc idProcessor) chan<- uint {
    ch := make(chan uint)
    for i := uint(0); i < limit; i++ {
        go func() {
            for {
                id, ok := <-ch
                if !ok {
                    return
                }
                proc(id)
            }
        }()
    }
    return ch
}

func main() {
    runtime.GOMAXPROCS(4)
    var wg sync.WaitGroup //this is just for the demo, otherwise main will return
    fn := func(id uint) {
        fmt.Println(id)
        wg.Done()
    }
    wg.Add(1000)
    ch := SpawnStuff(10, fn)
    for i := uint(0); i < 1000; i++ {
        ch <- i
    }
    close(ch) //should do this to make all the goroutines exit gracefully
    wg.Wait()
}

playground