Revert "Fixup: make signal handlers a bit simpler."

cmd/alertmanager/main.go

@@ -554,19 +554,31 @@ func run() int {
 	}()
 
 	var (
-		hup  = make(chan os.Signal, 1)
-		term = make(chan os.Signal, 1)
+		hup      = make(chan os.Signal, 1)
+		hupReady = make(chan bool)
+		term     = make(chan os.Signal, 1)
 	)
 	signal.Notify(hup, syscall.SIGHUP)
 	signal.Notify(term, os.Interrupt, syscall.SIGTERM)
 
+	go func() {
+		<-hupReady
+		for {
+			select {
+			case <-hup:
+				// ignore error, already logged in `reload()`
+				_ = configCoordinator.Reload()
+			case errc := <-webReload:
+				errc <- configCoordinator.Reload()
+			}
+		}
+	}()
+
+	// Wait for reload or termination signals.
+	close(hupReady) // Unblock SIGHUP handler.
+
 	for {
 		select {
-		case <-hup:
-			// ignore error, already logged in `reload()`
-			_ = configCoordinator.Reload()
-		case errc := <-webReload:
-			errc <- configCoordinator.Reload()
 		case <-term:
 			level.Info(logger).Log("msg", "Received SIGTERM, exiting gracefully...")
 			return 0