ioapp-proposal2.scala

import IOApp.Runtime

trait IOApp {
  // Implicit extractor
  implicit final def contextShift(implicit r: Runtime): ContextShift[IO] =
    r.contextShift
  
  // Implicit extractor
  implicit final def timer(implicit r: Runtime): Timer[IO] =
    r.timer
  
  def run(args: List[String])(implicit r: Runtime): IO[ExitCode]
  
  // ...
}

object IOApp {
  
  trait Runtime {
    def executionContext: ExecutionContext
    def timer: Timer[IO]
    def contextShift: ContextShift[IO]
  }
}