public ListenableFuture<Void> getCompletionFuture() {
        return doneFuture;
    }
Returns a future which completes when the rpc finishes.
The returned future fails if the rpc fails.

@return ListenableFuture future
shenyu-plugin/shenyu-plugin-proxy/shenyu-plugin-rpc/shenyu-plugin-grpc/src/main/java/org/apache/shenyu/plugin/grpc/proto/CompleteObserver.java