Godeps/_workspace/src/gopkg.in/mgo.v2/session.go
func (s *Session) Close() {
	s.m.Lock()
	if s.cluster_ != nil {
		debugf("Closing session %p", s)
		s.unsetSocket()
		s.cluster_.Release()
		s.cluster_ = nil
	}
	s.m.Unlock()
}
func (s *Session) Close() {
	s.m.Lock()
	if s.cluster_ != nil {
		debugf("Closing session %p", s)
		s.unsetSocket()
		s.cluster_.Release()
		s.cluster_ = nil
	}
	s.m.Unlock()
}
// Close terminates the session.  It's a runtime error to use a session
// after it has been closed.