chainntnfs: add unique ID field to track conf ntfns within notifier

chainntnfs/btcdnotify/btcd.go

@@ -61,6 +61,7 @@ type txUpdate struct {
 // notifications. Multiple concurrent clients are supported. All notifications
 // are achieved via non-blocking sends on client channels.
 type BtcdNotifier struct {
+	confClientCounter  uint64 // To be used aotmically.
 	spendClientCounter uint64 // To be used atomically.
 	epochClientCounter uint64 // To be used atomically.
 
@@ -800,6 +801,7 @@ func (b *BtcdNotifier) RegisterConfirmationsNtfn(txid *chainhash.Hash,
 
 	ntfn := &confirmationNotification{
 		ConfNtfn: chainntnfs.ConfNtfn{
+			ConfID:           atomic.AddUint64(&b.confClientCounter, 1),
 			TxID:             txid,
 			NumConfirmations: numConfs,
 			Event:            chainntnfs.NewConfirmationEvent(numConfs),