Should I go?

My coworker asked me to go watch a movie with him today but I have a boyfriend. I dont think my coworker knows I have a boyfriend. My boyfriend knows i have a lot of guy friends (I grew up with guys so im more comfortable with them) and he is okay with me being friends with them. Should I tell my coworker about my boyfriend first and see if he still wants to go? Or should I not go at all?