How to read Github Secrets into application.properties without using Spring Boot?

Question

I have a non Spring Boot Java application and want to store and read some secret keys using GitHub Secrets into my applications.properties file.

I have Base64 encoded the values and stored them in GH Secrets, and now I am trying to access them like so in my application.properties file:

com.stuff.some-prod-key=${{ secrets.SOME_PROD_KEY }}

However, when trying to use this syntax, the value will be ${{ secrets.SOME_PROD_KEY }} vs the actual value if I had hardcoded it into my application.properties file.

Is this possible to without Spring Boot? If so, do I need to have my properties file read it in from another file first or am I doing this completely wrong?