rate-limiting with waitGroup

rate-limit.go

// fetch images concurrently with set limits equal to cl
func fetchImages(imgs Images, cl int, put, del chan<- Img, w *sync.WaitGroup) {
	log.Printf("Total images to fetch %+v\n", len(imgs.List))
	// loop through all images and retrive them concurrently
	for i := 0; i < len(imgs.List); {
		w.Add(cl)
		for ii := 0; ii < cl; ii++ {
			img := imgs.List[i+ii]
			go getImg(img, imgs.GetImgName(i+ii), put, del, w)
		}
		w.Wait()
		i += cl
	}
}

// get particular image
func getImg(img Img, n string, out, del chan<- Img, w *sync.WaitGroup) {
	defer w.Done()
        ....
}