With the recent talk about Mozilla's persona authentication system (
https://developer.mozilla.org/en-US/docs/Persona) I figured I'd see how hard it would be to implement in Go and using some Gorilla libraries. Turns out it wasn't very hard at all. I've made the code available at
https://gist.github.com/3831610 in case anyone else wants to take a look.
I'm not sure if there would be any benefit of turning it in to a library as it's quite simple to implement and a fair bit of the functionality depends on client-side code, but hopefully the example is enough to get others started.
Let me know if you have any feedback :)