Dark Parts of the Universe by Samuel Miller

Outer Banks meets Bone Gap in New York Times bestselling author Samuel Miller's propulsive and genre-bending YA mystery, following a group of teenagers who discover a dead body while playing an app-based adventure game that sends players to "random" locations, unlocking a much deeper mystery about their small town.
In Calico Springs, Willie's life has been defined by two powerful forces: God and the river. The "miracle boy" died for five minutes as a young child, and ever since, Willie is certain he survived for a reason, but that purpose didn't become clear until he found the Game.
The Game is called Manifest Atlas, and the concept is simple: enter an intention and the Game provides a target-a blinking blue dot on the map. Willie's second time playing Manifest Atlas, his intention takes him to an ominous target: three empty graves. Willie is sure the Game is telling him he's going to die.
Willie's older brother, Bones, doesn't believe him, but their friends are intrigued. Sarai, a girl from across the river, sets the next intention: something bloody. The group follows the Game's coordinates and they discover something even more unsettling than the graves: a dead body. Sarai's stepfather's body. The Game is suddenly personal.
Willie is dedicated to proving the Game works while Sarai is set on finding out what happened to her stepdad. Bones just wants to enjoy his last summer before real life begins. As the group digs deeper into Manifest Atlas, stranger and wilder things begin to appear, unlocking a much deeper mystery running like an undercurrent through the small town.