private network gunicorn

Question

I am trying to connect to my flask api via private network, I've set this start command as per docs:
```gunicorn app:app --bind [::]:${PORT-3000}```

The API initializes fine, but when I try to send a request from my other api through the private network like this:
```
try:
        res = requests.post("http://master-api.railway.internal:3000/call")
        print(res.text)
        print(res.status_code)
        return {}, 200
    except Exception as e:
        print(e)
        False```

It gives me this error:
```HTTPConnectionPool(host='master-api.railway.internal', port=3000): Max retries exceeded with url: /call (Caused by NewConnectionError(': Failed to establish a new connection: [Errno 111] ECONNREFUSED'))```