Firebase Realtime Database query is very slow on MAC OS 10.x

### Please fill in the following fields:
Pre-built SDK from the [website](https://firebase.google.com/download/cpp) or open-source from this repo:
Firebase C++ SDK version: 6.12.0
Firebase plugins in use (Auth, Database, etc.): Auth, Realtime
Additional SDKs you are using (Facebook, AdMob, etc.): Facebook
Platform you are using the C++ SDK on (Mac, Windows, or Linux): **MAC**
Platform you are targeting (iOS, Android, and/or desktop): **MAC OS**

### Please describe the issue here:

Hi firebase team!

Currently, I'm querying the data on the MAC OS platform. I'm facing the problem as follows :

The query takes a long time (1 to 3 minutes) to return a response. So This affects the user experience of my app.

On the IOS, Android and Windows platforms all work very well. I only have this problem on MAC OS.

I also tested both link options x86_64 and universal. But this also could not help me solve this problem.

Here is the information regarding my project :

Xcode: 11.3.1

Firebase_cpp_sdk: [ as above ]

My query : ( same as on the IOS, Android and Windows platforms)

```
auto user = ap::Database::getInstance().getUserInfo();

firebase::database::DatabaseReference dbref = database->GetReference();

std::string path = cocos2d::StringUtils::format("users/%d/%s/", user._id, USER_REALTIME_VARIABLE);

auto result = dbref.Child(path).GetValue();

result.OnCompletion([callback](const Future& result_data) {

//my codes

});

```
As I know, MACOS doesn't officially support from firebase team, right?
Could the firebase team help me solve this issue?
Hopefully, I can get answers soon from your side.
### Please answer the following, if applicable:
Have you been able to reproduce this issue with just the [Firebase C++ quickstarts](https://github.com/firebase/quickstart-cpp)? No, I have not tried.
What's the issue repro rate? 100%