12 year old boy is trapped in limbo

I remember watching this movie a few times on Netflix around 2012-2014, give or take a year or two. This boy is roller skating with his friend along the train tracks over a river and he slips and falls in. When he opens his eyes he's in this kind if limbo. Which I think was a version of his neighborhood/town. He meets this girl his age who's in a coma and for some reason his grandpa is there. The ending scene is them confronting whatever entity is keeping them there in this big top tent. Oh, and he had this love of space and wanted to be an astronaut because his dad had loved space.