Limiting the number of running goroutines using semaphores in #golang

limit_goroutines_with_semaphores.go

var (
  concurrency = 5
  semaChan = make(chan struct{}, concurrency)
)

func doWork(item int) {
  semaChan <- struct{}{} // block while full
  go func() {
    defer func() {
      <-semaChan // read releases a slot
    }()
    // work
    log.Println(item)
    time.Sleep(1 * time.Second)
  }()
}

func main(){
  for i := 0; i <= 1000; i++ {
    doWork(i)
  }
}