I'm not sure and this is one of the reasons that stops me from suicide. What if you're punished in some way? What if you go to an even worse place you can't kill yourself to escape? Like the afterlife in His Dark Materials.
My ex last year said to me "When you die there's nothing, can you honestly tell me that's what you'd want" I said that would be amazing, I'd love it. She didn't even have words for how little she understood and just looked horrified.
I'm not afraid of death though, I don't even understand why a lot of people are, I guess they enjoy life more. Immortality would be my idea of torture, you're trapped here forever then. The thought of death being worse than life prevents me from choosing it, but if it happens on it's own then I look forward to finding out where I go.