How to fix "the response was already sent" error in Elixir

If you get an "(Plug.Conn.AlreadySentError) the response was already sent" error: ```elixir Server: localhost:4000 (http) Request: POST /api/v1/xxx ** (exit) an exception was raised: ** (Plug.Conn.AlreadySentError) the response was already sent (plug) lib/plug/conn.ex:332: Plug.Conn.put_status/2 ``` Verify that you have not defined the action plug more than once: ``` plug :action ```