Google had four canonical languages: C++, Go, Java, and Python. They are defined internally in an engineering handbook. There is no such similar style guide for Go, as a a lot of what the existing guides say is "don't use x." If that were needed for Go we would have failed.
It is not listed here:
http://google-styleguide.googlecode.com/svn/trunk/
These guides are much more than just what gofmt does.
In a Google IO conference talk someone stated that the Google App Engine support was actually made by the Go team.
Not all new APIs released by Google tend to offer Go APIs as well from day 1.
So I miss the official language support that you say already exists.