accounts: process requests before stopping service

Ensure that we don't stop the service while we're processing a request.
This is especially important to ensure that we don't stop the service
exactly after a user has made an rpc call to send a payment we can't
know the payment hash for prior to the actual payment being sent
(i.e. Keysend or SendToRoute). This is because if we stop the service
after the send request has been sent to lnd, but before TrackPayment
has been called, we won't be able to track the payment and debit the
account.

Author: ViktorT-11

accounts/service.go

@@ -214,6 +214,18 @@ func (s *InterceptorService) Start(lightningClient lndclient.LightningClient,
 
 // Stop shuts down the account service.
 func (s *InterceptorService) Stop() error {
+	// We need to lock the request mutex to ensure that we don't stop the
+	// service while we're processing a request.
+	// This is especially important to ensure that we don't stop the service
+	// exactly after a user has made an rpc call to send a payment we can't
+	// know the payment hash for prior to the actual payment being sent
+	// (i.e. Keysend or SendToRoute). This is because if we stop the service
+	// after the send request has been sent to lnd, but before TrackPayment
+	// has been called, we won't be able to track the payment and debit the
+	// account.
+	s.requestMtx.Lock()
+	defer s.requestMtx.Unlock()
+
 	s.contextCancel()
 	close(s.quit)