Add module or package naming

[palash25]

This seems to be missing from the doc. A lot of new gophers might have questions about whether to name the module containing internal APIs pkg or internal or what should be the name of the module that contains helper functions for e.g. utils

[Pungyeon]

Thanks for the feedback @palash25 🙏 I will try to include this as soon as I have some extra time :)