PROTON-2843: [Go] Fix segfault on settling a message on closed receivers

Deliveries can not be settled after the receiver has been freed. Therefore, this adds a check to ensure that the receiver was not closed (which ensures that `Free` has not been called on the link yet)

go/pkg/electron/electron_test.go

@@ -331,3 +331,18 @@ func TestHeartbeat(t *testing.T) {
 		t.Error("expected server side  time-out or connection abort error")
 	}
 }
+
+func TestReceiverCloseBeforeAcknowledge(t *testing.T) {
+	p := newPipe(t, nil, nil)
+	defer func() { p.close() }()
+	r, s := p.receiver(Source("foo"))
+	go func() {
+		out := s.SendSync(amqp.NewMessageWith(0))
+		_ = test.ErrorIf(t, test.Differ(Closed, out.Error))
+	}()
+	rm, err := r.Receive()
+	test.FatalIf(t, err)
+	r.Close(nil)
+	<-r.Done()
+	_ = test.ErrorIf(t, test.Differ(Closed, rm.Accept()))
+}

go/pkg/electron/receiver.go

@@ -28,7 +28,6 @@ import (
 )
 
 // Receiver is a Link that receives messages.
-//
 type Receiver interface {
 	Endpoint
 	LinkSettings
@@ -201,10 +200,19 @@ type ReceivedMessage struct {
 
 // Acknowledge a ReceivedMessage with the given delivery status.
 func (rm *ReceivedMessage) acknowledge(status uint64) error {
-	return rm.receiver.(*receiver).engine().Inject(func() {
-		// Deliveries are valid as long as the connection is, unless settled.
-		rm.pDelivery.SettleAs(uint64(status))
+	receiverError := make(chan error)
+	err := rm.receiver.(*receiver).engine().Inject(func() {
+		// Deliveries are valid as long as the receiver is, unless settled.
+		err := rm.receiver.Error()
+		receiverError <- err
+		if err == nil {
+			rm.pDelivery.SettleAs(status)
+		}
 	})
+	if err != nil {
+		return err
+	}
+	return <-receiverError
 }
 
 // Accept tells the sender that we take responsibility for processing the message.