首先是dubbo的泛化广播调用，泛化调用方式为GSON
然后不是有个全链路追踪插件叫 sofa-tracer 嘛，sofa-tracer的dubbo filter拦截器工作时候，要从 RpcContext.getUrl()，但是发现get出来是个空导致空指针
![image](https://user-images.githubusercontent.com/42512469/195077820-0731c73e-bb4f-4088-9142-8e3abbde29c1.png)

但是我用常规自带的广播调用模式，就没问题，只有 broadcastCluster1Invoker 有问题
        <dependency>
            <groupId>org.apache.dubbo.extensions</groupId>
            <artifactId>dubbo-cluster-broadcast-1</artifactId>
            <version>1.0.0</version>
            <scope>provided</scope>
        </dependency>
就是上面这种，有问题
*
     * @return null if the underlying protocol doesn't provide support for getting response or the response is not of the specified type
     */
    @Override
    @SuppressWarnings("unchecked")
    public <T> T getResponse(Class<T> clazz) {
        return (response != null && clazz.isAssignableFrom(response.getClass())) ? (T) response : null;
    }
    /**
     * is provider side.
     *
     * @return provider side.
     */
    @Override
    public boolean isProviderSide() {
        return !isConsumerSide();
    }
    /**
     * is consumer side.
     *
     * @return consumer side.
     */
    @Override
    public boolean isConsumerSide() {
        return getUrl().getSide(PROVIDER_SIDE).equals(CONSUMER_SIDE);
    }
    /**
     * get CompletableFuture.
     *
     * @param <T>