code: func (m *wsNotificationManager) NotifyMempoolTx(tx *btcutil.Tx, isNew bool) {
  	n := &notificationTxAcceptedByMempool{
  		isNew: isNew,
  		tx:    tx,
  	}
  
  	// As NotifyMempoolTx will be called by mempool and the RPC server
  	// may no longer be running, use a select statement to unblock
  	// enqueuing the notification once the RPC server has begun
  	// shutting down.
  	select {
  	case m.queueNotification <- n:
  	case <-m.quit:
  	}
  }
docs: // NotifyMempoolTx passes a transaction accepted by mempool to the
  // notification manager for transaction notification processing.  If
  // isNew is true, the tx is is a new transaction, rather than one
  // added to the mempool during a reorg.