code: func (l *AdvisoryLock) CancelPending() error {
  	_, err := l.tx.Exec(`SELECT pg_cancel_backend(pending.pid)
  				FROM (SELECT pid 
  					FROM pg_locks 
  					WHERE locktype = 'advisory' 
  					AND granted = 'f' 
  					AND objid = $1) as pending`, l.key)
  	if err != nil {
  		return fmt.Errorf("error canceling pending locks: %v", err)
  	}
  	return nil
  }
docs: // CancelPending cancels any pending advisory locks (those that are not yet
  // granted) for this advisory lock key.
  //
  // This can be useful in situations where you only want a maximum of 1 process
  // waiting to obtain the lock at any time.