select

select.ss

(define chan-1 (make-chan))
(define chan-2 (make-chan))

(go (chan<- chan-1 'hello-chan-1))
(go (chan<- chan-2 'hello-chan-2))

; sleep for 20 millisecond
(sleep 20)

(select
  ((<-chan chan-1))
  ((<-chan chan-2))
  (default 'hello-default))

(close-chan chan-1)
(close-chan chan-2)

; the output will be randomized: hello-chan-1 or hello-chan-2