Add on_handled callback. Triggered after processing, but before sendi…

…ng the response.

README.md

@@ -56,6 +56,12 @@ execute(Req, Env) ->
             fun(Ctx) ->
                 % Perform anything after well-formedness check of your request
                 % Examples are parsing the query args, or authentication
+                Ctx
+            end,
+        on_handled =>
+            fun(Ctx) ->
+                % Perform anything after processing, before sending the result.
+                Ctx
             end
     },
     % Handle the request, returns updated Req and Env for next Cowboy middleware

src/cowmachine.erl

@@ -73,7 +73,11 @@ request_1(Controller, Req, Env, Options, Context) ->
         Context1 = cowmachine_req:set_env(EnvInit, Context),
         case cowmachine_decision_core:handle_request(State, Context1) of
             {_Finish, _StateResult, ContextResult} ->
-                cowmachine_response:send_response(ContextResult);
+                ContextResult1 = case maps:get(on_handled, Options, undefined) of
+                    undefined -> ContextResult;
+                    Fun when is_function(Fun) -> Fun(ContextResult)
+                end,
+                cowmachine_response:send_response(ContextResult1);
             {upgrade, UpgradeFun, _StateResult, ContextResult} ->
                 {upgrade, UpgradeFun, _StateResult, ContextResult}
         end