Results in e.g.
2021/11/17 14:50:33 downstream "127.0.0.1:53292": failed to write message: write tcp 127.0.0.1:6667->127.0.0.1:53292: use of closed network connection
2021/11/17 14:50:33 downstream "127.0.0.1:53292": connection closed
Instead, we should only close the reading side of the connection in conn.Close, and close the writing side in the outgoing message goroutine.
Simon Ser referenced this ticket in commit d423a1c.