That sounds a bit backwards, you would need to implement the network protocol twice and keep them in sync - which can be very tricky... Having a common code-base for parsing the network protocol into internal game structure objects is a huge advantage...

A big chunck of AAA game servers is already implemented in Java, .NET, Erlang.

Not all of them use C++ on the server side.

Many of them use C++ libs with language bindings for 'common' code though. And let that just be one of the weakest points of Go...

Yeah, that could be the case yes.

I think it's treated as being just fine for video game servers, my assumption was that they meant for game engine development.