Did you have him since he was a puppy? Are you intentionally taking his food away (that can cause food guarding)? If you try to take their food away just to prove you can, the dog learns not to trust you.
I would start with hand feeding him. Then anytime my hand would come near the bowl would be to drop more food into it not take it away. I would also practice NILF. I did this with a four month old foster dog that I had who would growl when I went near his food. He was a Pit/Golden/Chow mix and it worked. But it takes time and patience. Until this dog, I had no idea a young dog could be like this. It was a learning experience to say the least as none of my own dogs guarded things from me.
I had all my own dogs at eight weeks and I would make them sit before I fed them. I didn't mess with their food while they were eating, I would drop more food into their bowls with my hands and hand feed them. I've never had a food guarding dog doing that.