It's being worked on for Go 1.4 (scheduled to release in December). It's the primary feature they want to get done for that release. There was a talk about in back in May[0]. rcs is working on c2go to convert the existing compiler to Go[1][2].

[0] http://www.confreaks.com/videos/3432-gophercon2014-go-from-c...

[1] https://code.google.com/p/rsc/source/list

[2] https://code.google.com/p/rsc/source/browse/#hg%2Fc2go