It sounds like he could have a thyroid problem. It is very common in Golden's and very reasonable to treat. Make an appointment with your vet and describe they symptoms and ask that they run a thyroid panel. If he is low (hypothyroid) your vet will put him on medication, pills twice a day most likely. You will notice an improvement in the skin issues fairly soon, The fur takes longer, about 6 months.
My Murphy has hypothyroid and his hair thinned terribly and he has those weird black patches on his skin. They cleared up quickly. His coat is now beautiful and his energy also increased. He has been on meds now about three years. They aren't terribly expensive but must remain on them for life. Also they need to have their blood tested every 6 months to make sure they are receiving he proper amount of medication as somtimes their levels change during the course of treatment.
I strongly recommend you have him tested as it is very common and very easily treated.
Good luck!
My Murphy has hypothyroid and his hair thinned terribly and he has those weird black patches on his skin. They cleared up quickly. His coat is now beautiful and his energy also increased. He has been on meds now about three years. They aren't terribly expensive but must remain on them for life. Also they need to have their blood tested every 6 months to make sure they are receiving he proper amount of medication as somtimes their levels change during the course of treatment.
I strongly recommend you have him tested as it is very common and very easily treated.
Good luck!