I understand about your situation. Here is how you deal with it. Call/ or text every day or at least every week once. Keep yourself busy, work and school, and spend time with other friends or make new friends. If this guy is truly your best friend, that will never change. I moved away from family and friends including my best friend who is my family's tenet in our house. I still talk and text the guy at least every two or 3 days. My wonderful partner whom I live with, his best friend is in Georgia and we live in California. They have been best buds for 20 years. I have been best buds with my buddy for over 5 years. If he is your best friend, time and distance knows no bounds. Sometimes people get busy so don't get angry if he doesn't respond to you right away. You have no idea what he is doing when he leaves and vice versa. Other than that, Good Luck and stay in touch with him.
be in touch, respect his choice for moving, you will find good friends again