GCP OAuth: How to access user's email address?

Hello All. I deployed a Streamlit-based app to the GCP using App Engine and Docker. My app is restricted to the internal users via Google consent screen. The user needs to be signed in in their company’s Google account to be able to use the app. All of that works just fine, what I’m struggling with is getting an email address of the user.

I went through the documentation and it seems that I need to get the authorization code and then obtain an access token. However, after trying different approaches I could not find a working solution.

Does anyone have experience in doing something similar?