Snippet 7 for https://medium.com/@francesc/why-are-there-nil-channels-in-go-9877cc0b2308

main.go

func merge(a, b <-chan int) <-chan int {
	c := make(chan int)
	go func() {
		defer close(c)
		for a != nil || b != nil {
			select {
			case v, ok := <-a:
				if !ok {
					fmt.Println("a is done")
					a = nil
					continue
				}
				c <- v
			case v, ok := <-b:
				if !ok {
					fmt.Println("b is done")
					b = nil
					continue
				}
				c <- v
			}
		}
	}()
	return c
}