Not tested, but can use first, and need recur to not consume stack?

core.async-lazy-sequence

(use 'clojure.core.async)


;this is the function you want to use
(defn lazy-channels [chs]
  (lazy-seq
    (cons (first (alts!! chs))
          (recur chs))))


;now for the tesging
(def chs [ (chan) (chan) (chan) ]) ; the channels can come from anywhere, here we are using three channels for testing

(thread (dotimes [i 1000]
         (>!! (rand-nth chs) (str "m-" i)))) ;add 1000 elements to a random selection of channels

;create a sequence
(def s (lazy-channels chs))
;now consume, please note that this will block when no more data is available on the channels
(doseq [msg s]
     (prn msg))