gotenv

Supports loading from multiple .env files where the first value wins, as demonstrated in the Load function with filenames like ".env.production" and "credentials".

Allows applying variables from any io.Reader, such as strings or network streams, using the Apply function, offering flexibility beyond file-based sources.

Provides separate functions (Load/Apply vs OverLoad/OverApply) to choose whether to override existing environment variables, ensuring predictable behavior.

Includes a Must helper that panics on errors, enabling applications to fail quickly during startup if configuration is missing or invalid.