static WebSocketClientBuilder builder(SessionProtocol protocol, EndpointGroup endpointGroup) {
        requireNonNull(protocol, "protocol");
        return builder(Scheme.of(SerializationFormat.WS, protocol), endpointGroup);
    }
Returns a new {@link WebSocketClientBuilder} created with the specified {@link SessionProtocol}
and the {@link EndpointGroup}.
core/src/main/java/com/linecorp/armeria/client/websocket/WebSocketClient.java