Six months is still relatively young for socialization - you have at least another six months to introduce him to the world.
That being said, my dog was not properly socialized with other dogs (I adopted him as an adult, otherwise he'd be perfect
). He is good with people, but we have been working on his dog manners for six months now. He's a lot better, but has a ways to go, at least another six months. However, I've heard it said that a lot of that is genetic. I believe my dog would always have been somewhat shy. A dog with normal social drives should adapt very quickly, providing that he has not been abused. And even an animal with a very difficult past can re-learn to trust the world, if you put in the work.