public WebSocketClient build() {
        final WebClient webClient = buildWebClient();
        return new DefaultWebSocketClient(webClient, maxFramePayloadLength, allowMaskMismatch, subprotocols,
                                          aggregateContinuation);
    }
Returns a newly-created {@link WebSocketClient} based on the properties of this builder.
core/src/main/java/com/linecorp/armeria/client/websocket/WebSocketClientBuilder.java