@Override
            public ProxyConfig select(SessionProtocol protocol, Endpoint endpoint) {
                return ProxyConfig.socks4(socksProxyServer.address());
            }
Tests if a request is failed with {@link SessionProtocolNegotiationException} if a session negotiation
with the backend server takes longer than a connection timeout.

<p>Cleartext protocol are not used because the session could immediately complete when a connection is
established with the proxy server.
core/src/test/java/com/linecorp/armeria/client/proxy/ProxyClientIntegrationTest.java