how to reset the env when hot code change

[HillCool]

thank you for notice, here is the situation. i have a release project named V1.0.1, and i want to use rebar3 upgrade, everything is ok ,but when i rebar3 attach ,the project can't read the env due to collapse,i try to use application:get_env ,it is undefined. Actually, i set the env in my supervisor (the top level in monitor tree),so can you tell me how to solve this problem ?
i find some doc about file appup, but not relup, should i add something setting in the relup? here is what i found about appup, watting you answer
https://medium.com/@kansi/hot-code-loading-with-erlang-and-rebar3-8252af16605b

[ferd]

This is something that Erlang/OTP does automatically; it resets the environment values to whatever was in (in order): command line arguments > sys.config > .app's env

There is no workaround aside from storing dynamic configuration under a name like myapp_dymamic which won't get reset -- only the variables of existing loaded applications get reset.

[HillCool]

@ferd ，thank you for your answer, i solve my problem by change the appup file, i modify appup file to load moudle ，and apply {M,F,A} ,it help me reset env, last is rebar3 relup ,get a relup file , and then ,it is work