My golden retreiver is 12 months n he doesn't want to eat dog food (royal canin for golden puppy) by himself. He is healthy just spoiled. I try to let him eat by himself n not feed him, but it has been 3 days n still refused eating. Finally I mixed his dog food with human food, was grilled chicken n he ate a lot, but I am not happy with that, I just want him to eat dog foods. How is this, what should I do?

I don't think he should be on puppy food any longer. Buy him an adult dog food and he may eat. Not a good idea to mix with human food, you are correct there. He will expect this all the time. I don't think you should worry, he will eat when he is ready. He just wants something tasty.

Tick

I made the same mistake with mine when he refused to eat, I started mixing all sorts of yummy foods in with his dog food and then of course, he expected it all the time.
I ended up feeding a wet food for dinner and making his breakfast of dry food seem like a treat. I would get super excited about it and give him just a few pieces by hand as a reward. I then started putting just a small amount on the floor or on a plate so it still seemed like a treat, not just regular food, and so eventually when I gave it to him in his regular bowl he gobbled it all up thinking it was still a treat.

You could also try soaking the dry for a short amount of time in a little low sodium chicken stock, the longer you soak it, the softer the dry will become so you just want it soaking long enough to absorb some of the chicken flavor.