Hi Loic,

when gun:shutdown/1 is called on HTTP/2, it causes a GOAWAY frame with reason INTERNAL_ERROR to be sent to the server. The expected message is GOAWAY with reason NO_ERROR.

I though I had implemented the shutdown handling in Gun, but I see now that you did it in #206. (I did it in cowboy.)

Anyway, I traced it as follows: gun:shutdown/1 → closing(status(State, shutdown), shutdown) → Protocol:closing(Reason, _, _, _), so gun_http2:closing/4 is called with reason 'shutdown', but only reasons 'normal' and 'owner_down' cause a GOAWAY frame with reason NO_ERROR. Any other reason (including shutdown) causes a GOAWAY frame with reason INTERNAL_ERROR.

closing(Reason0, State=#http2_state{socket=Socket, transport=Transport,
		http2_machine=HTTP2Machine}, _, EvHandlerState) ->
	Reason = case Reason0 of
		normal -> no_error;
		owner_down -> no_error;
		_ -> internal_error
	end,

The simple fix would be to add shutdown -> no_error here.

In gun_ws there is specific handling for reason 'shutdown' which suggests this is the right way to fix it.

closing(Reason, State, EvHandler, EvHandlerState) ->
	Code = case Reason of
		normal -> 1000;
		owner_down -> 1001;
		shutdown -> 1001;
		{error, badframe} -> 1002;
		{error, badencoding} -> 1007
	end,

I checked for tests covering this, but the gun initiated shutdown tests in shutdown_SUITE all use cowboy as the server, so the messages are not checked byte-by-byte.