Why, outside of loops, do you need in in swift?

Question

Swift

Here for example

router.get("/") {
    request, response, next in
    response.send("Hello, World!")
    next()
}

Answer 1

The start of the closure's body is introduced by the in keyword. This keyword indicates that the definition of the closure's parameters and return type has finished, and the body of the closure is about to begin.

closures