code: func (s *session) AuthID() *identity.ID {
  	s.mutex.Lock()
  	defer s.mutex.Unlock()
  
  	if s.auth == nil {
  		return nil
  	}
  
  	return s.auth.GetID()
  }
docs: // AuthID returns the ID representing the object used for authorization (e.g.
  // user or machine token).