Warning: soapbox lecture follows. Read ahead at your own risk
A harness will teach your dog nothing. If you simply want to restrain your dog, good luck to you. If you want to train your dog, then use a device that will allow training to occur.
The go-to device for big dogs that pull is the prong collar. These things are power steering for dogs. They allow you provide corrective stimulus that is very similar to what real dogs provide to each other in the real world. They allow one to use the least force and are therefore far safer and more humane than something that chokes your dog. Yes, they look medieval. So what?
Goldens, and Lab's, are responsible for winning more obedience competitions than any other breeds. Your Golden wants to please you. You just need to know how to communicate to him when he's doing it wrong, and when he's doing it right. Get a prong. Get a bait (treat) bag. Get some high quality training that shows you how and when to apply prong corrections (you don't simply pull continuously on a prong, that doesn't work either) or treat rewards (balanced training). You will be heeling everywhere on a loose lead in no time.
Taught my neighbor, and neighbor's Golden, how to do this in only 30 minutes (after the Golden pulled her over and broke her ankle. After years of thinking I was torturing my dog with a prong, she could not believe the difference, not only for herself, but for her dog, who became much happier now that communications were clearer.
Restraining is not training!