(defmacro defstage [stagename & body]
  `(defn ~stagename [~'caller]
      (let [~'trxn (atom [])]
        ~@body
        (forward ~'caller @~'trxn)))
  `(swap! *services* #(assoc % (name '~stagename) ~stagename)))

(defmacro go [stagename args]
  `(swap! ~'trxn #(conj % [~stagename ~args])))

(defstage foobar
  (go :ftp  {:host "ftp-host"}))