I'm going to let go of the door when there's someone right behind me
Why would you let go of the door when someone is behind you?
I want to let go of it quickly and move on, I have things to do.
It's rude not to hold doors open for others. It's especially childish to do that deliberately. You should practice good social etiquette.
I'm going to let go of the door and close it right in front of the person who's trying to get in and then walk away.
Would you like if someone did the same thing to you? If other people see this they might ask you to leave to treating the other visitors poorly.