Having worked on even medium sized projects in golang, I started to appreciate why Java requires that. The golang code base was a mess, struct declarations and their implementations littered all over the place, making it hard to follow what's going on. You then need and IDE, and hope that those structs do not accidentally implement some random interface because of structural typing.

Interesting that you mention interfaces. Mostly I like Go, but one of my bugbears is the difficulty of finding out which interfaces are implemented by a type. It's much easier in Java. Java file organisation is more consistent and regular which is a win at scale.