If you really want to know it isn't for finding the main site that everyone uses golang it is for finding all other references to the language.
As an example cloudflare writes a large amount of posts that have something to do with go if you google "go cloudflare" you get relevant results but you also get results of google mixing in the word "get" for go which are completely irrelevent.
Now if you google "golang cloudflare" all results pertain to the Go programming language.
(Not the best example because cloudflare doesn't use golang in their posts).
How hard is that?