Go is one of those languages where "good layout" feels more elusive to me than in other languages. I think you accidentally highlight one of the reasons why.

    core.WeatherServices

Which makes sense because you're using a lot of things from core but since I have to carry the package name around everywhere I use it, outside of that module, it becomes a bit of a strain.

    weather.Service

Would clearly be a better name in the "go style," but the single level package structure always makes me feel like my types are dangling out in space outside of any decent hierarchy.

I love Go as a language but I dislike how often it makes me think of exceptionally tiny things like this. Please don't read this as a criticism of your project just a general criticism of how thin the Go "namespace" ideology actually is.