Yeah, I think whatever structure works for you is what is best. It’s hard to prescribe any sort of “best practices” in terms of folder structure since people can have wildly varying use cases. I don’t have a great example in golang, but the “complex architecture” that I always link to is MIT’s Open Learning infra (in python, but conceptually should be equivalent).
https://github.com/mitodl/ol-infrastructure
But I still think what works for you is what is “best”.