My OS is my IDE. For everything else, there's the go tool, which does testing and now renaming, too [1].
The debugger would be nice, and Delve is a great start it looks like -- but I can't tell for sure since it still isn't compatible with OS X.
[1]: https://groups.google.com/d/msg/golang-nuts/96hGPXYfqsM/WreO...