Currently, I have decided to use Python and JavaScript (especially React and Node.js) for any of my projects. Well, I have used Python with Django for a lot of things, and I would certainly recommend Django to anyone, due to its high secure authentication and authorization inbuilt system, a ready to use admin platform, template tags, and many more. Well, I guess that you would like to use Python to create the backend of your application, an API, and React Native for the frontend. Python and JavaScript (React) are on the trend these days and have a huge community, so there are many resources, tutorials, great documentation. I have not really heard anyone using Flutter and Go for applications these days, so I would not recommend it to you, it would make your life much more difficult.

Hope that helps, and good luck with your project!