I see the following message in my Elixir logs periodically:

Unexpected message: {:ssl_closed, {:sslsocket, {:gen_tcp, #Port<0.9056>, :tls_connection, :undefined}, #PID<0.10027.10>}}

That looks like a close message from the SSL socket, which I'd expect hackney to manage the same as a close of the TCP connection (which are handled properly). I'm using the async option to stream the response data as it comes in.