The dog wouldn't want to die without him. Dogs are almost like our symbiotes.

Even though I’d set up the cat tree on her insistence, Donut jumped straight onto my neck and settled in.

“Goodnight, Carl,” she said.

“Goodnight, Donut,” I said, patting her head.

“Promise me you won’t let me die alone like GumGum’s mom,” she said. “Or GumGum. I guess she died alone, too. She was probably really scared.”

“Don’t worry, Donut,” I said. “We’ll find out who’s responsible, and we’ll make them pay.”

I'm just reading the "Dungeon Crawler Carl" series (which includes "The Dungeon Anarchist's Cookbook") and he sort of inherits his ex-girlfriends cat Donut. Then the earth is flattened by aliens because we failed to file and appeal 50 years after first content and Carl is forced into a Running Man style dungeon for the alien's entertainment. Luckily his cat Donut evolves and becomes intelligent and can shoot magic missiles out of her eyes. She later says:

“You promised me that I wouldn’t die alone,” she said. “You can’t keep that promise if you die before me. We do this together.”