public String getWebSocketMessage() {
        try {
            return BLOCKING_QUEUE.poll(10, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
get the return message from the server.
@return String String
shenyu-e2e/shenyu-e2e-client/src/main/java/org/apache/shenyu/e2e/client/gateway/GatewayClient.java