better.clj

(defn handle-error [url status error]
  (println (format "Error getting %s" url))
  (println (format "Status returned: %d" status))
  (println (format "Error: %s" error)))

(defn process-response [url headers body]
  (println (format "Getting URL %s" url))
  (println (format "Last modified: %s" (:last-modified headers)))
  (println (format "Body is: %d bytes long" (count body)))
  url)

(defn callback-wiki [url]
  (http/get url
            (fn [{:keys [status headers body error]}]
              (if error
                (handle-error url status error)
                (process-response url headers body)))))

(defn pages-list [start end]
  (map #(format "https://en.wikipedia.org/wiki/%d" %) (range start end)))

(defn -main []
  (let [futures (doall (map callback-wiki (pages-list 0 5)))]
    (doseq [resp futures]
      (println (format "Processed: %s" @resp)))))