lzmadec is a Go package for extracting files out of .7z files using 7z program.
Short tutorial: http://blog.kowalczyk.info/article/g/Extracting-files-from-7z-archives-in-Go.html
API reference: http://godoc.org/github.com/kjk/lzmadec
Hopefully this is temporary hack and some day https://github.com/uli-go/xz will offer this functionality in pure Go code.