lntest: ensure we always cancel active streaming notifications

lntest/node.go

@@ -639,9 +639,9 @@ func (hn *HarnessNode) lightningNetworkWatcher() {
 	go func() {
 		defer hn.wg.Done()
 
-		ctxb := context.Background()
 		req := &lnrpc.GraphTopologySubscription{}
-		topologyClient, err := hn.SubscribeChannelGraph(ctxb, req)
+		ctx, cancelFunc := context.WithCancel(context.Background())
+		topologyClient, err := hn.SubscribeChannelGraph(ctx, req)
 		if err != nil {
 			// We panic here in case of an error as failure to
 			// create the topology client will cause all subsequent
@@ -650,6 +650,8 @@ func (hn *HarnessNode) lightningNetworkWatcher() {
 				"client: %v", err))
 		}
 
+		defer cancelFunc()
+
 		for {
 			update, err := topologyClient.Recv()
 			if err == io.EOF {