What about Go makes it easy to manage and refactor large codebases? I don't do much Java, but whenever I've watched someone use Eclipse for refactoring, I question why I'm still using vim, because it is just magic and does everything for you.
Secondarily, gofmt makes code very standardized and easy to skim. It takes Python's 'only one (obvious) way to do it' one or two steps further, by forcing everyone to to write their code the same way. This makes refactoring a lot easier because you don't need to read as much code each time in order to understand what's going on (or at least, you can mentally parse it much faster).
Finally, the context-free grammar combined with a strong, static type system means that migrating code from an old (incompatible) version of Go to the most recent one can be done painlessly with the 'go fix' tool. This isn't your py2to3 tool - this accepts valid (old) Go code as input and reliably produces valid (up-to-date) Go code as the output.
That last bit isn't actually used in refactoring manually, but I make note of it because very few languages give you anything close to this level of reliability with code modification, which speaks volumes about the design of the language's grammar.
I don't want to use a language that doesn't come with a parser in the standard library anymore.
`gofmt -r 'InitialName -> FinalName'`