private Http2ClientConnectionHandler newHttp2ConnectionHandler(Channel ch, SessionProtocol protocol) {
        final Http2Connection connection = new DefaultHttp2Connection(/* server */ false);
        final Http2ConnectionEncoder encoder = encoder(connection);
        final Http2ConnectionDecoder decoder = decoder(connection, encoder);

        final Http2ClientConnectionHandlerBuilder builder =
                new Http2ClientConnectionHandlerBuilder(ch, clientFactory, protocol);
        return builder.codec(decoder, encoder)
                      .initialSettings(http2Settings())
                      .build();
    }
A handler that closes an HTTP/2 connection when the server responds with an HTTP/1 response, so that
HTTP/1 is used instead of HTTP/2 on next connection attempt.
core/src/main/java/com/linecorp/armeria/client/HttpClientPipelineConfigurator.java