Somebody in the #go-nuts irc channel has a Go syntax file for gedit, so I would ask there if you want that.
I personally use what Rob Pike and Russ Cox use: acme. And I know Ken Thompson still uses sam.
Edit: For those interested, I have created a page to collect Go syntax highlighting files for various text editors. If you have any that is not included there let me know and I'll be happy to add it.