Last time I checked this was the main thing that was missing for Go (a complete, multi platform GUI lib). Has there anything like this arisen yet? Some quick googling points to Gothic, which sounds promising.
Im working in a weird "application platform"(looks more like a crazy userspace OS) right now and as a step 2, im planning to bind to the chrome compositor in the low level.. and build a ui framework in Go from there.. but the phase 1 is really the most important, and i think i will pre-launch before the UI kit..
The good side of it, is that you can also bind a web rendering engine totally coded in Go or bind the webkit rendering to the compositor backend..