if it bounces back it is a dead ball.

"ARTICLE 5. a. Each goal shall consist of two white or yellow uprights extending
at least 30 feet above the ground with a connecting white or yellow horizontal
crossbar, the top of which is 10 feet above the ground. The inside of the uprights
and crossbar shall be in the same vertical plane as the inside edge of the end line.
*Each goal is out of bounds.* "

"ARTICLE 3. A live ball becomes dead and an official shall sound their whistle
or declare it dead:
a. When it goes out of bounds *other than a kick that scores a field goal after
touching the uprights or crossbar*; when a ball carrier is out of bounds;
or when a ball carrier is so held that their forward progress is stopped.
When in question, the ball is dead (A.R. 4-2-1-II)."