Brutally close connection on gun_down

Similar reason as for the ratelimiter

Author: jchristgit

lib/nostrum/shard/event.ex

@@ -21,8 +21,7 @@ defmodule Nostrum.Shard.Event do
     if payload.t == :READY do
       Logger.info("READY")
 
-      {%{state | session: payload.d.session_id, resume_gateway: payload.d.resume_gateway_url},
-       []}
+      {%{state | session: payload.d.session_id, resume_gateway: payload.d.resume_gateway_url}, []}
     else
       {state, []}
     end

lib/nostrum/shard/session.ex

@@ -266,7 +266,11 @@ defmodule Nostrum.Shard.Session do
         %{conn: conn} = data
       ) do
     Logger.info("Lost complete shard connection. Attempting reconnect.")
-    :gun.flush(conn)
+    # Brutally close to make sure we don't mess up the state machine
+    # due to gun reconnecting automatically. For the WebSocket disconnect
+    # case, this is fine.
+    :ok = :gun.close(conn)
+    :ok = :gun.flush(conn)
     connect = {:next_event, :internal, :connect}
     {:next_state, :disconnected, %{data | conn: nil, stream: nil}, connect}
   end