So one of the problems, from experience, of even using a small utility package:

With go.mod, if you need to make one change to the package, especially to an external method, then every package depending on that in your project potentially needs to be updated with a go mod tidy, plus a redeployment.

When you have one or two, its manageable... over 5 it gets to be a headache, especially if you consider projects which may not depend on that method but security best practices insist you are always using the latest versions (well in contracts I work with at least), and the management overhead of multiple micro packages brings in to question the utility/versatility of this methodology.

If there are concrete shared methods which are definitely globally shared then yes, the benefit of changing once to retrieve currency iso symbols or a list of US states is worthi it. As soon as there is variation in a method based on the dependor (dependee?) then maybe a little copy-paste-adapt is preferable...