You want to get variables from local variables

Dieses Issue hat keine Beschreibung.

The issue title suggests expanding variables from local shell variables, not just environment variables. Start by reading the main.go entry point and the substitution logic in the envsubst package. Look for where environment variables are currently fetched and consider adding a flag or mode to also read from local shell state. Check existing tests to understand the expected behavior and add new test cases for local variable expansion.

Vom Indexierungsmodell aus dem Issue-Text verfasst.