First I was so surprised to read that there's another Golden Retriever Cookie!!! That's the name of my Golden baby too.

I experience, that Cookie likes to challange me when it comes to the 'come' command. She knows it very well and comes most of the time. But now that she's starting to really grow up, she likes to see how far she can push it.
What we learn in the obedience classes, is to turn around and walk/run away when the dog isn't coming. The dog normally won't stay if you go away.
I always give plenty of attention to Cookie when she comes, giving a little snack and a cuddle.

There has a topic about how to get your dog to come to you when you call her: just wondering