a kid too afraid to die alone and a father makes a rash promise

[Joshua]

i'm trying to find a book. i've tried searching for the plot on google and nothing book related. it's a book about a little girl who is dying and she's afraid to die alone. so her father blurts out rashly that he will die with her. incredibly powerful story with final words that will break you i don't care who you are.

[Michele]

adult book or YA? do you recall where/when the story is set?