mount thoughts on: https://github.com/danielsz/system/blob/master/src/system/components/jdbc.clj

1. jdbc.clj

(defn connect [db-spec] 
  (jdbc/get-connection db-spec))

(defn disconnect [conn] 
  (.close conn))

2. example.clj

(:require [app.jdbc :as jdbc]        ;; << that defined above
          [app.env :as env])

(defstate db :start (jdbc/connect (get-in env [:source :db]))
             :stop (jdbc/disconnect db))