Session expiry isn't forwarded to the client

When the join session expires, the server hangs up on the client (websocket) and logs the following error `Session timeout exceeded`.
This exact error should also be visible on the client side. But instead the client seems to see only `⨯ Error: Failed to read join confirmation: websocket: close 1006 (abnormal closure): unexpected EOF` which is misleading and indicates we don't properly handle close on the websocket client side.