[randomdata]

The difference is that the regexp is embedded in your code as part of your code and won't change after you've shipped your code. It can only panic if your code is flawed. If the compiler was smarter, it'd be a compiler error. It only ends up a runtime concern because the compiler isn't smart enough to interpret your regular expressions to find your mistakes.

If you were loading the regexp from an alterable file at runtime, to allow the user to change it after the program is shipped, you wouldn't use regexp.MustCompile. You would use regexp.Compile and gracefully deal with any errors that the user may have made.

If you are talking about compile-time configuration, where once your program is built it won't change, why would you use YAML when you could simply use language-native variables/constants with actual compile-time safety? Regexps can improve on some programming problems over writing the equivalent code, so it's a good tradeoff in some cases. YAML is never nicer than the equivalent code.

[mirekrusin]

This config file is likely mounted in container, possibly different on different environemnts - ie. not "embedded", not "known at compile time".

[randomdata]

And so failure is a user mistake, not a programmer mistake, and should be handled as such. The programmer and the user being the same person is irrelevant.

[mirekrusin]

The difference is that the config is loaded at bootstrap stage - if it fails, starting service fails, there is not much to handle other than crash and supervisor (ie. k8s or whatever) will try to start it again.

[randomdata]

You would likely exit. Crashing on invalid user input would be nonsensical.