code: func (l *Lock) createSession() (string, error) {
  	session := l.c.Session()
  	se := l.opts.SessionOpts
  	if se == nil {
  		se = &SessionEntry{
  			Name: l.opts.SessionName,
  			TTL:  l.opts.SessionTTL,
  		}
  	}
  	id, _, err := session.Create(se, nil)
  	if err != nil {
  		return "", err
  	}
  	return id, nil
  }
docs: // createSession is used to create a new managed session