There are many good approaches to handle configuration in a modern application. Now we use such things as configuration files, environment variables, command-line parameters, as well as CI configuration patterns and on-fly config file builds, remote config servers, specific mapping, and binding services and even more complex things.

But the target is the same - provide the app with a configuration, which is fast to get and easy to use. But how to do that?

There are many concurrent approaches to organize application configuration nowadays.

Classic .ini files, .json, .toml, .yaml, configs, modern .env and, of course, container environment. And don’t forget about CLI arguments! Am I missing something?

Let me be honest, I really dislike any implicitness in interfaces. Same for the CLI of course. Any of your interfaces, whether public or internal, API or object interface, a class method or module facade – they have to cooperate fair. The contract between you and the other side should be explicit, rightful and without any notes in small text at the bottom of the page.