Hereafter (2020)

Tod, Piper, and Eric promised their best friend, boyfriend, and brother respectively, Mark, before he committed suicide. They wouldn't remember him in the traditional sense, at a headstone in a graveyard. No, they would eat psychedelic mushrooms from his corpse in a grave beside his parent's lakeside cabin in an attempt to commune across realms. What they learn is a lot more than what they bargained for.