@Override
    public synchronized void onCompleted() {
        doneFuture.set(null);
    }
A holding a future which completes when the rpc terminates.
shenyu-plugin/shenyu-plugin-proxy/shenyu-plugin-rpc/shenyu-plugin-grpc/src/main/java/org/apache/shenyu/plugin/grpc/proto/CompleteObserver.java