[Fawndallas]

I too have a resource guarder (not a golden). Here is how I handled it.
1. Food - Start by making it very clear that the food comes from you and doesn't just appear. This takes time and effort on your part, but it went a long way in managing/ resolving the issue with food. To do this,
1.a) You hand feed. This can go on for a week, but it must be every meal. It is ok to use a glove to protect your fingers from the shark teeth. If they try to snatch, close your hand. If they growl, close your hand. They don't get the food till they are nice. This needs to be every bite of the food. Put just enough in your hand that you can comfortably close around. This is very time consuming, but it was worth it, as it resolved most of the issue.
1.b) Nothing in Life is Free - To get anything, including food, including the food in your hand for above, the dog must do something. It is as simple as a "sit." This teaches 2 things: Manners and Self Control. Puppies have neither until taught. This progresses to the manner training to wait until you say it is ok to eat. This also progresses to many other well mannered things including getting out of a vehicle, going in or out of a door, and so much more. For now though, focus on meals / food. This doesn't take long. Just remember the short attention span and to give the food quickly.
2. Resource guarding other things - As soon as it happens, no matter what it is, that item gets put up. You don't need to say anything. Just pick up the item and put it up. This needs to be done in front of them. This teaches that the behavior they gave resulted in play time being over and all fun and games comes to a stop. This takes a little bit longer as the attention span for a puppy is extremely short. This must be consistent, by everyone and everywhere and every time. Every time they are allowed to continue playing or with the good times, it reinforces the incorrect behavior. You can also put them in their bed, but a word of caution here. The dog senses your emotions. It is very easy for a dog to translate going to bed/crate as a discipline and then you have a whole different set of issues to resolve. If you want to do this, I recommend 1st putting the item up, spend a minute or 2 ignoring the dog (collecting your thoughts/emotions), then put the dog in their bed/crate with no words spoken.

Above needs to be done by all adults in the house, not just the primary caretaker. Dogs are smart. They easily figure out who is a "push over" in the home. If you have kids, I recommend waiting for this issue to be resolved before interaction. As I said, dogs figure out who is a push over very quickly. Your dog snapping for any reason needs to be unacceptable behavior where everything fun immediately stops, including feeding. If it continues, you are putting yourself/others in a situation that could result in a bad dog bite.

Good luck. If you want more information or more details, find me on FaceBook. We can message.

 

[Fawndallas]

How do you put up the item when he's resource guarding it?

For my home:
First, if I am concerned about getting bit, that is the 1st issue I address. That take priority over resolving the guarding issue. For that, you need to see a professional trainer (not a pet store training session). That is not something that can be addressed behind a computer. Meantime, the dog does not get free access to anything but water and bed. Free access only encourages the problem and every day will make it worse to resolve. If not addressed, someone will get seriously hurt.
Once the getting bit issue is resolved, then I address the resource guarding. This is tailored to the dog in front of me. For some, a simple "drop" and "leave it" is all it takes. For others, if they do not know these commands, a firm "no" and then I take the toy.
If they run off with the item, then the situation has changed from a teaching moment to a game with them. I simply walk away and ignore them. This has taught me that they cannot have that item yet. I simply wait for them to drop the item; then I get it and put it up. This hasn't worked on the guarding problem, but it also doesn't reinforce the bad behavior. Then we go back a few steps in the training. This is where the feeding by hand comes into play. That method teaches many things. For toys, the "feeding by hand" still works, just modified. They only get the toy when you are engaging them. You start the play session, you also end the play session. I wouldn't recommend having a fetch/retrieve session, as they will simply either run off with the toy or start guarding it; neither do you have control in. A game of tug is good for this training session. Teaching "drop" and "leave it" are vital tools to learn.
If they start guarding large items, that are clearly not for dogs, (like your bed, couch) then they don't get access to those luxuries. It make require having a leash on the dog when loose in the home. With the leash, you can remove them from the off limits item.
Look into Michael Elise or Susan Garrett training videos. They have a good balanced way of training and their methods are effective. Understand, if you are only on the 100% positive training side, Susan leans more this way. Michael is more balanced and deals mostly with protection dogs, but many of his instructions are good for companion homes.

 

[Fawndallas]

He’s not a toaster that I’ve just bought that I can just give back. That has serious implications for me, namely that I have really bonded with him and he’s a lovely boy otherwise and my kids also adore him. I was just really hoping that someone would tell me this is something that we can work through and there is light at the end of the tunnel.

For most dogs, yes, you can get through this. It takes lots of focus and dedication. As you know and others have said, it is not common for this breed to be aggressive. At a computer glance, your dog just seems like one that has gotten away with bad behavior and now it has escalated to something that could get dangerous. You should get a good trainer to help you; not one that does big training classes. This needs to have one on one sessions. Look into bird hunting clubs, they are a good resource for finding trainers tailored to the breed.

 

[Fawndallas]

Have you considered the possibility that the resource he is guarding is actually you, and not the food? In your description at the top of the page, food is in the picture every time, but so are you. I ask the question because at one point my last golden would treat me as a resource to be guarded, and while she was never overtly aggressive towards humans, she would make it clear that I was "hers", and she was aggressive to other dogs that approached me. She would have been around your dog's age at the time - the early "teenage" years. It was dealt with fairly easily by making sure she knew that I called the shots, not her, and that I didn't need guarding.

Good point and definitely something else for the OP to consider.