What does "goner" mean?

Someone (or something) doomed; a hopeless case, especially someone who is bound to die soon.

Goner

Common synonyms include: dead man walking, doomed person, doomed project, gosling, hopeless case, lost cause.

/ˈɡɒnə(ɹ)/ noun, slang

noun, slang ·Moderate ·College level

Noun

1
Someone (or something) doomed; a hopeless case, especially someone who is bound to die soon. informal
"I'm a goner if this plan doesn't work."
2
a person in desperate straits; someone doomed wordnet
3
A ball hit out of the playing area for a home run. slang

"For a second there I thought I was a goner."

From gone + -er. First attestations around 1850.