lndclient: close trackpayment channels once final state is reached

When the server is finsihed sending updates in trackPayment, we get an
EOF error. To allow clients to listen on these channels after the
payment has succeeded, we close them to signal that we have finsihed
sending updates.

lndclient/router_client.go

@@ -5,6 +5,7 @@ import (
 	"crypto/rand"
 	"encoding/hex"
 	"fmt"
+	"io"
 	"time"
 
 	"github.com/btcsuite/btcutil"
@@ -225,6 +226,8 @@ func (r *routerClient) TrackPayment(ctx context.Context,
 
 // trackPayment takes an update stream from either a SendPayment or a
 // TrackPayment rpc call and converts it into distinct update and error streams.
+// Once the payment reaches a final state, the status and error channels will
+// be closed to signal that we are finished sending into them.
 func (r *routerClient) trackPayment(ctx context.Context,
 	stream routerrpc.Router_TrackPaymentV2Client) (chan PaymentStatus,
 	chan error, error) {
@@ -235,6 +238,17 @@ func (r *routerClient) trackPayment(ctx context.Context,
 		for {
 			payment, err := stream.Recv()
 			if err != nil {
+				// If we get an EOF error, the payment has
+				// reached a final state and the server is
+				// finished sending us updates. We close both
+				// channels to signal that we are done sending
+				// values on them and return.
+				if err == io.EOF {
+					close(statusChan)
+					close(errorChan)
+					return
+				}
+
 				switch status.Convert(err).Code() {
 
 				// NotFound is only expected as a response to