bugfix: graceful consumer shutdown

Author: eric-chao

consume.go

@@ -84,26 +84,26 @@ func NewConsumer(
 // Run starts consuming with automatic reconnection handling. Do not reuse the
 // consumer for anything other than to close it.
 func (consumer *Consumer) Run(handler Handler) error {
-	err := consumer.startGoroutines(
-		handler,
-		consumer.options,
-	)
-	if err != nil {
-		return err
-	}
-
-	handler = func(d Delivery) (action Action) {
+	handlerWrapper := func(d Delivery) (action Action) {
 		if !consumer.handlerMu.TryRLock() {
 			return NackRequeue
 		}
 		defer consumer.handlerMu.RUnlock()
 		return handler(d)
 	}
 
+	err := consumer.startGoroutines(
+		handlerWrapper,
+		consumer.options,
+	)
+	if err != nil {
+		return err
+	}
+
 	for err := range consumer.reconnectErrCh {
 		consumer.options.Logger.Infof("successful consumer recovery from: %v", err)
 		err = consumer.startGoroutines(
-			handler,
+			handlerWrapper,
 			consumer.options,
 		)
 		if err != nil {