I have functions that have to deal with hierarchical data objects, JSON like things. All collections are identically typed (although they have optional fields, different length arrays, etc.), but there is more than one type. In order to write simple code, I wanted to write one function that gets them from the database, one to update a single record, one to notify of changes, etc. So my top-level type to cover all of these collections is map[string]interface{}, which in TypeScript would be Map<string, any>.

Then I ran unit tests, and sometimes a weird error cropped up. Turns out I made an error in an append: instead of concatenating two arrays, I added the second array as the last element of the first. That was a time consuming bummer.

This problem could have been prevented by two approaches: copying every function for every type, or generics.

Go is a nice language, which makes some tasks easy to implement, almost fool proof, but it still lacks in other areas.