gistfile1.clj

(def pause-chan (async/chan))

(defn pause! []
  (let [pause-end-chan (async/chan)]
    (async/put! pause-chan pause-end-chan)
    (fn []
      (async/put! pause-end-chan :whatever))))

(async/go-loop []
  (let [[pause _] (async/alts! [pause-chan] :default nil)]
    (when pause 
      (async/<! pause))) ; take to pause the go-loop
  (println "doing some work")
  (async/<! (async/timeout 2000))
  (println "done some work")
  (recur))

(def unpause! (pause!))