My instinct tells me that somehow it would have to be converted to a string or byte[] (which might even be the same things in Go?) and then saved to disk.
The gob package will let you serialize maps. I wrote up a small example http://play.golang.org/p/6dX5SMdVtr demonstrating both encoding and decoding maps. Just as a heads up, the gob package can't encode everything, such as channels.
Edit: Also string and []byte are not the same in Go.