pronunciation - Isn't a “gonner” or “gonna” slang for a person about to die?

(I think this "blank" moment of mine is what is called in AmEng a brain fart, so be it)

Isn't ‘a gonner/gonna’ slang for a person who is about to die? It's said in situations where, potentially, someone risks getting themselves killed. Maybe children also use it when play acting. I'm sure there must be something similar but the dictionary entries tell me that ‘gonna’ is a contraction of "going to" and ‘gonner’ is not listed in The Free Dictionary.

For example:

If you do that (a dangerous thing) you're a gonner

I presume a gonna or a gonner (or something similar) is short for “a person who is going to die”.

Answer

Gonner is a rare spelling variant of goner.

Goner

TFD n. slang One that is ruined or doomed.
"I'm a goner if this plan doesn't work"

M-W n. someone or something that is going to die or that can no longer be used
"This old computer is a goner. We'll have to get a new one.
"

Wiktionary etymology: gone +‎ -er