The backwards compatibility promises of Go definitely makes upgrading a breeze. Java is pretty much in the same boat (except it maintains bytecode compatibility instead of source). When working with languages that don’t offer these promises it’s always a nightmare to upgrade to newer versions.
Not quite what you’re looking for, but Google does have an official style guide which may be slightly helpful
The go stdlib uses it a lot. For example, the strings package
Much needed change, I wish they made it apply for all go versions though