fix: channel-safety in StopWatch and signal handling

cmd/speedle-ads/main.go

@@ -122,7 +122,7 @@ func main() {
 		// Do not close errChan: the second goroutine may still send to it.
 	case <-intChan:
 		log.Info("Interrupt signal")
-		close(intChan)
+		signal.Stop(intChan)
 	}
 
 	log.Info("Stopping servers...")

cmd/speedle-pms/main.go

@@ -119,7 +119,7 @@ func main() {
 		// Do not close errChan: the second goroutine may still send to it.
 	case <-intChan:
 		log.Info("Interrupt signal")
-		close(intChan)
+		signal.Stop(intChan)
 	}
 
 	log.Info("Stopping servers...")

pkg/store/etcd/etcdStore.go

@@ -623,7 +623,9 @@ func (s *Store) Watch() (pms.StorageChangeChannel, error) {
 				log.Errorf("panic in Watch outer goroutine: %v", r)
 			}
 			close(evalChan)
-			close(s.stop)
+			// Note: s.stop is closed by StopWatch (guarded by stopOnce), not
+			// here, so a panic in this goroutine cannot leave a later
+			// StopWatch sending on an already-closed channel.
 			close(errChan)
 			close(stopChan)
 			s.wg.Done()
@@ -762,7 +764,10 @@ func watch(evalChan chan pms.StoreChangeEvent, s *Store, errChan chan error, sto
 func (s *Store) StopWatch() {
 	s.stopOnce.Do(func() {
 		if s.stop != nil {
-			s.stop <- struct{}{}
+			// Close (not send) so every inner watch goroutine's
+			// `case <-s.stop` fires; a single send would only wake one of
+			// them. stopOnce makes this idempotent and panic-safe.
+			close(s.stop)
 		}
 	})
 }

pkg/store/file/fileStore.go

@@ -356,7 +356,9 @@ func (s *Store) Watch() (pms.StorageChangeChannel, error) {
 			}
 			watcher.Close()
 			close(storeChangeChan)
-			close(s.stop)
+			// Note: s.stop is closed by StopWatch (guarded by stopOnce), not
+			// here, so a panic in this goroutine cannot leave a later
+			// StopWatch sending on an already-closed channel.
 		}()
 		for {
 			select {
@@ -406,7 +408,9 @@ func (s *Store) Watch() (pms.StorageChangeChannel, error) {
 func (s *Store) StopWatch() {
 	s.stopOnce.Do(func() {
 		if s.stop != nil {
-			s.stop <- struct{}{}
+			// Close (not send) so the watch goroutine's `case <-s.stop`
+			// fires immediately. stopOnce makes this idempotent and safe.
+			close(s.stop)
 		}
 	})
 }