add s.noMessageCallback function for SQS receiveMessage to callback w…

…hen no message is received from the queue

aws/sqs/sqs.go

@@ -24,7 +24,8 @@ type Raw struct {
 }
 
 type SQS struct {
-	client *sqs.Client
+	client            *sqs.Client
+	noMessageCallback func() //callback function to call when no message is reveived from the queue
 }
 
 // New returns an SQS struct which wraps an SQS client using the default AWS credentials chain.
@@ -89,6 +90,11 @@ func (s *SQS) Ready() bool {
 	return s.client != nil
 }
 
+// Setter method for emptyMessageCallback
+func (s *SQS) SetNoMessageCallback(callback func()) {
+	s.noMessageCallback = callback
+}
+
 // Receive receives a raw message or error from the queue.
 // After a successful receive the message will be in flight
 // until it is either deleted or the visibility timeout expires
@@ -135,6 +141,9 @@ func (s *SQS) receiveMessage(ctx context.Context, input *sqs.ReceiveMessageInput
 		switch {
 		case r == nil || len(r.Messages) == 0:
 			// no message received
+			if s.noMessageCallback != nil {
+				s.noMessageCallback()
+			}
 			continue
 		case len(r.Messages) == 1:
 			raw := r.Messages[0]