Ping-pong game with core.async

ping_pong.clj

(ns ping-pong
  (:require [clojure.core.async :as async :refer [<!! >!!]]))

(defn ping [ch]
  (println "Ping")
  (>!! ch :ping)
  (<!! (async/timeout 500)))

(defn pong [ch]
  (println "Pong")
  (>!! ch :pong)
  (<!! (async/timeout 500)))

(defn return [ch]
  (let [ball (<!! ch)]
    (if (= ball :ping)
      (pong ch)
      (ping ch))))

(defn play []
  (let [ch (async/chan 1)]
    (loop [cnt 0]
      (if (= cnt 0)
        (ping ch)
        (return ch))
      (if (< cnt 10)
        (recur (inc cnt))
        (println "Game over!")))))