Golang Fan-in concurrency pattern.

fanin.go

func fanIn(chans ...<-chan int) chan int {
	var wg sync.WaitGroup

	c := make(chan int)

	// Closure to send values from a channel
	output := func(ch <-chan int) {
		for n := range ch {
			c <- n
		}
		wg.Done()
	}

	wg.Add(len(chans))

	// send values on c via differnt goroutines
	for _, ch := range chans {
		go output(ch)
	}

	// wait for all goroutines to finish before closing the channel
	go func() {
		wg.Wait()
		close(c)
	}()

	return c
}