Handling different environments in Docker for .Net core and CI/CD

We are currently running Azure Devops Server for CD/CI. We have a build step and a release step, normal setup. If the release steps we to a token replacement for our appsettings.json from the artifacts in the build step.

But if we are moving to Docker container all the code and appsettings.json are inside the resulting images, created from the build step. I dont want to have one build step per environment. How to I solve this? Do I have to throw my appsettings.json and only use environment variables, read appsettings.json from a mounted volume?

(In this question Im now talking about non-secrets)

Source: StackOverflow