code: func (s *SQLStore) DeleteClient(clientID string) error {
  	s.Lock()
  	_, err := s.preparedStmts[sqlDeleteClient].Exec(clientID)
  	if err != nil {
  		err = sqlStmtError(sqlDeleteClient, err)
  	}
  	s.Unlock()
  	return err
  }
docs: // DeleteClient implements the Store interface