Godeps/_workspace/src/gopkg.in/mgo.v2/session.go
func (s *Session) Copy() *Session {
	s.m.Lock()
	scopy := copySession(s, true)
	s.m.Unlock()
	scopy.Refresh()
	return scopy
}
func (s *Session) Copy() *Session {
	s.m.Lock()
	scopy := copySession(s, true)
	s.m.Unlock()
	scopy.Refresh()
	return scopy
}
// Copy works just like New, but preserves the exact authentication
// information from the original session.