I've been using Java since it was released, and (at the same time) Go for several years now.

The amount of cognitive overhead in dealing with all the history that's baked into Java is really annoying. Things like the dated concurrency model, the overachieving in logging (and other) libraries (when one to use?), the poorly thought out I/O libraries, the crazy build tools and slow builds, ... It's always a relief to get back the the smoothness of Go.