Crate training

I rescued a 6 month old Golden. I have been getting him comfortable with his crate by leaving toys and treat in crate. He was even going in on his own to take a nap.
   
Then I started closing him in. He barked and cried for a bit, then stopped. I am trying to do this everyday for about an hour so that I will be able to leave him in his crate if I need to go out.
   
My question is..... now that I have started locking him in, he no longer goes in to nap there by himself. He only goes in when I put treats inside and then close the door. Am I doing this process correctly? I want to be able to put him in his crate occasionly to keep him safe and to keep my house safe. Thanks

When i crate trained both of my dogs. I did the samething as you so you are doing good. everytime I wanted my dog to go to the crate I would tell him to go to bed I also stopped putting treats in there, cause everytime he would get into trouble I would tell him to go to bed and lock the crate, just for alittle bit insted of spanking him. It kind of like grounding a kid. after a few weeks he would go to the crate when he was tired or if he thought he was in trouble. hope this helps!