Sadly, in the age of the internet, that’s just not really possible. Endgame leaked online ahead of the premiere and hours later, the Russos released a statement asking people to keep all spoilers to themselves. After all, it’s one thing to seek spoilers for yourself, but it’s wrong to force them on people who don’t.
Article source: https://www.cinemablend.com/news/2470932/man-reportedly-beaten-outside-cinema-for-shouting-avengers-endgame-spoilers