The standard godoc documentation browser does this too when started with the -analysis option. They all use the same source code oracle functionality available from the x/tools repo.
Thanks for the correction. I think that's somewhat unfortunate, though. The powerful shared tooling is one of the strengths of the Go ecosystem and if there are issues with it that prevent the use in Goland I'd rather see those get fixed.
OTOH, they (Jetbrains) probably have shared infrastructure (between languages) within their IDE code base, too, and are more comfortable using their existing tooling.