Wiktionary
go out like a light
vb. (context simile English) To fall asleep quickly.
Usage examples of "go out like a light".
LaFollet had been terrified that they were going to lose her, that she was simply going to go out like a light, but somehow she'd survived.
LaFollet had been terrified that they were going to lose her, that she was simply going to go out like a light, but somehow she’.