IIRC, Canonical joined the go community around 2010/2011 when docker has not been created. They are actually one of the early adopters of Go. Some major projects from Canonical using Go are juju[0], mgo[1], etc.
Edit: format.
Edit: format.
and in the course of juju, canonical wrote client libraries for quite a few clouds as they didn't exist at the time.
openstack -> https://github.com/go-goose/goose (imho the best one out there.)
goamz -> http://github.com/go-amz/go-amz (many forks of this one, aws is going to use a different auto gen'd one for forthcoming official go sdk)
azure -> https://launchpad.net/gwacl (imho the best one out there.)
Perhaps Go becomes the language for Ubuntu Phone apps ?