go concurrency

gistfile1.txt

func restore(repos []string) error {
	errChan := make(chan error, 1)
	sem := make(chan int, 4) // four jobs at once
	var wg sync.WaitGroup
	wg.Add(len(repos))
	for _, repo := range repos {
		sem <- 1
		go func() {
			defer func() {
				wg.Done()
				<-sem
			}()
			if err := fetch(repo); err != nil {
				errChan <- err
			}
		}()
	}
	wg.Wait()
	close(sem)
	close(errChan)
	return <-errChan
}