What do you do if you don't really want to keep in touch with someone but don't want to be rude?

Tell him to take a long walk on a shot pier , tell him to gedafukoutahere, tell him your boyfriend who was in prison for breaking the legs on this guy who just looked at you is coming home, tell him you just found out you got an STD .
I mean what da fuck does he know ? It’s all a lie anyway