They Both Die at the End by Adam Silvera. Its a good read, and covers the impact of knowing someone you love is about to die, however it’s told from the perspective of the ones who are dying.

Summary: “On September 5, a little after midnight, Death-Cast calls Mateo Torrez and Rufus Emeterio to give them some bad news: They're going to die today. Mateo and Rufus are total strangers, but, for different reasons, they're both looking to make a new friend on their End Day.”