While the switch to go modules was pretty smooth on the code front, the tooling was another matter. They had to rewrite everything to support modules and decided to create this concept of a "language server" which would then be universal across languages and help editors like VSCode support new languages that pop up as long as they provide their own language server that matches the spec.

It's a nice idea but has been (and continues to be) super painful for anybody actually trying to get work done. This was a huge fuckup on the part of the Google engineers to combine the rewrite with module support. They should have first added module support to the existing tools THEN bitten off the totally new paradigm of a language server. Yes it would have been more total work but so many person-years of productivity was lost with the approach they took and we are still counting.