I need help learning the keys.

I have been trying to figure out way to learn what the keys are made up of for the longest time now. I feel that this one thing is the barrier to my progress at the moment. I am looking for a way to learn what makes up each key, besides just sitting down with a chart and memorizing it all. For example how do I figure out what is in Gmajor? Like what is sharp, what is minor or major. I feel like there has to be a pattern, or way to figure it out without actually hammering stuff down with memorization.