This isn't exactly "close to dying", but when I was around 10 years old, I was jumping on my mom's friend's son's trampoline in Sweden, having fun. I decided to try to do a front (or back??) flip on the trampoline (i've done it before successfully), and it ended pretty badly. I managed to land straight on my back and knock all the air out of my system. I couldn't breath for a full 5-10 seconds, but then I began to regain the ability to breath. It was pretty scary at the time.