In Rails, we use .env files for parameterization of the applications. This way, we can easily test locally and when we deploy to Heroku or Kubernetes, we can manage database connection details and etc by changing the container environment variables and ignoring the .env.

How does it work in C#? I see the appsettings.json, but configuration is often mixed with parameterization.

Is there any guide in making my .NET Core Web API compliant with the 12-factor app manifesto?