future-cancelled?

core.clj

(ns test-app.core)

(defn do-it-slow!
  [sleep-time]
  (Thread/sleep sleep-time))

(defn mk-future
  [sleep-time]
  (future (do-it-slow! sleep-time)))

(defn kill-future
  [f delay]
  (future
    (Thread/sleep delay)
    (future-cancel f)))

(def f (mk-future 10000))

(try
  (kill-future f 1000)
  (println "derefing future, will be blocked")
  (deref f)
  (catch Exception e
    (if (future-cancelled? f)
      (println "future was cancelled while blocking at deref")
      (throw e))))