How do you know you had that dream "just before you woke up?" You might have had it anytime during the night.
Having a dream about your job probably means that the job is highly meaningful for you and you think a lot about it during the day. It is a very habitual 'play of your mind.'
Years ago, when I was an aeradio operator (lot like an air-traffic controller) I used to have my mind filled both throughout the day and into a lot of my dreaming because, I think, the importance, excitement, involvement and investment in this part of my life. If your job plays a big part in your life, it's very likely you'll both think and dream about it a lot.