подскажите почему так
(def server-not-once-atom (atom nil))
=> #'gateway-api.core/server-not-once-atom
@server-not-once-atom
=> nil
(reset! server-not-once-atom 5)
=> 5
@server-not-once-atom
=> 5
(defonce server-not-once-atom (atom nil))
=> nil
@server-not-once-atom
=> 5