$ boot dev
boot.user=> (require '[mount.core :as mount]
'[issue-104.core :as iss]
'[clojure.tools.namespace.repl :as tn])
boot.user=> iss/teststate
#object[mount.core.DerefableState 0x7367eb6b {:status :pending, :val nil}]
boot.user=> (mount/start)
{:started ["#'issue-104.core/teststate"]}
boot.user=> iss/teststate
#object[mount.core.DerefableState 0x7367eb6b {:status :ready, :val "hi"}]
boot.user=> @iss/teststate
"hi"
boot.user=> (tn/refresh)
:reloading ()
:ok
boot.user=> iss/teststate
#object[mount.core.DerefableState 0x7367eb6b {:status :ready, :val "hi"}]
boot.user=> @iss/teststate
"hi"