(inaka#123) Close the connection after receiving 204 responses

In case of receiving an http answer with answer code 204, shotgun will
return the result from the server, but the connection is automatically
closed after receiving this answer.

src/shotgun.erl

@@ -503,12 +503,12 @@ wait_response({gun_response, _Pid, _StreamRef, fin, StatusCode, Headers},
                 gen_fsm:reply(From, {ok, Response}),
                 queue:in(Response, Responses)
         end,
-    {next_state, at_rest, State#{responses => NewResponses}, 0};
+    check_no_content_resp(StatusCode, State#{responses => NewResponses});
 wait_response({gun_response, _Pid, _StreamRef, nofin, StatusCode, Headers},
               #{from := From, stream := StreamRef, async := Async} = State) ->
     StateName =
       case lists:keyfind(<<"transfer-encoding">>, 1, Headers) of
-          {<<"transfer-encoding">>, <<"chunked">>} when Async == true->
+          {<<"transfer-encoding">>, <<"chunked">>} when Async =:= true->
               Result = {ok, StreamRef},
               gen_fsm:reply(From, Result),
               receive_chunk;
@@ -548,7 +548,7 @@ receive_data({gun_data, _Pid, _StreamRef, fin, Data},
                     body => NewData
                    }},
     gen_fsm:reply(From, Result),
-    {next_state, at_rest, State, 0};
+    check_no_content_resp(StatusCode, State);
 receive_data({gun_error, _Pid, StreamRef, _Reason},
              #{stream := StreamRef} = State) ->
     {next_state, at_rest, State, 0}.
@@ -558,11 +558,12 @@ receive_data({gun_error, _Pid, StreamRef, _Reason},
 -spec receive_chunk(term(), term()) -> term().
 receive_chunk({'DOWN', _, _, _, _Reason}, _State) ->
     error(incomplete);
-receive_chunk({gun_data, _Pid, StreamRef, IsFin, Data}, State) ->
+receive_chunk({gun_data, _Pid, StreamRef, IsFin, Data},
+              #{status_code := StatusCode} = State) ->
     NewState = manage_chunk(IsFin, StreamRef, Data, State),
     case IsFin of
         fin ->
-            {next_state, at_rest, NewState, 0};
+            check_no_content_resp(StatusCode, NewState);
         nofin ->
             {next_state, receive_chunk, NewState}
     end;
@@ -756,3 +757,12 @@ unexpected_event_warning(StateName, Event) ->
     error_logger:warning_msg( "Unexpected event in state '~p': ~p~n"
                             , [StateName, Event]
                             ).
+
+%% @private
+check_no_content_resp(StatusCode, State) ->
+    case StatusCode of
+        204 ->
+            {stop, no_content, State};
+        _ ->
+            {next_state, at_rest, State, 0}
+    end.