It’s never too early to build a relationship with your coach. Remember, coaches are human just like the rest of us no matter how much it can seem otherwise.
Getting to know the coach early has extra benefits as well. They will probably have training regimes or skill exercises that you can ask for in order to put yourself in the best possible position to succeed when you finally arrive. Not only that but the more the coach knows about you and your situation the better he will be able to give you good advice and mentor you. The coach is the one that can put you in contact with other players on the team and let you start building relationships with your teammates before you even arrive at school.
Remember, your coach will always have your best interest at heart and you can always look to them for guidance and advice, so be sure to establish that relationship and get to know one another.