GRPC CompletableFuture

@Override
public void getUserInfo(UserInfoRequest request, StreamObserver<UserInfo> response) {
  final CompletableFuture<String> Result =
      provider.getUserInfo(request.getUserId()); // some other grpc request invoke
  final CompletableFuture<UserInfo> responseFuture =
      trackResult.thenApply(result -> UserInfo.newBuilder().setUserInfo(result).build());
  responseFuture.whenComplete(
      (result, throwable) -> {
        if (result != null) {
          response.onNext(result);
          response.onCompleted();
        } else if (throwable != null) {
          response.onError(throwable);
        }
      });
}