Block a caller on any number of long-running/non-terminating functions continuing when any one of them returns (the others will run to completion, or presumably get cleaned up by the calling context):

wait-any.clj

;;; block caller until any one of the passed functions complets and return its result
(defn wait-any [& fns]
  (let [p (promise)]
    (doseq [f fns] (future (deliver p (f))))
    (deref p)))

;;; (wait-any #(do (Thread/sleep 4000) 1) #(do (Thread/sleep 2000) 2) #(do (Thread/sleep 3000) 3))
;;; output: 2 

(defn task [f] (go (f)))

(defn wait-any [& fs]
  (first (alts!! (into [] (map task fs)))))

;; (wait-any #(do (Thread/sleep 4000) 1) #(do (Thread/sleep 2000) 2) #(do (Thread/sleep 3000) 3))
;; output: 2