cr_15954.go

func doWork(s string, ch <-chan struct{}, wg *sync.WaitGroup) {
  defer func() {
    <-ch // free up space in the semaphore
    wg.Done() // tell the WaitGroup we're finished
  }()
  
  fmt.Println(s) 
}

func execute(work []string) {
  wg := &sync.WaitGroup{}
  sema := make(chan struct{}, 10) // concurrency limit of 10
  
  for _, url := range work {
    // if there are 10 items in flight, channel is full / will block
    // unblocks when a worker finishes
    sema <- struct{}{}
    
    wg.Add(1)
    go doWork(url, sema)
  }
  
  // close the channel as nothing else should write
  close(sema)
  
  // wait for all goroutines to finish
  wg.Wait()
}