TODO

Session.scala

import cats.{Monad, StackSafeMonad}
import cats.effect.{IO, LiftIO}

trait Session {
  def close(): Unit
}

case class SessionContext[T](exec: Session => IO[T]) {

  def runSession(newSession: () => Session): IO[T] = {
    val session = newSession()
    exec(session).map { t =>
      session.close()
      t
    }
  }

}

object SessionContext {

  implicit val instance: Monad[SessionContext] with LiftIO[SessionContext] =
    new StackSafeMonad[SessionContext] with LiftIO[SessionContext] {
      override def pure[A](a: A): SessionContext[A] =
        SessionContext(Function.const(IO.pure(a)))

      override def flatMap[A, B](fa: SessionContext[A])
                                (f: A => SessionContext[B]): SessionContext[B] =
        SessionContext(session => fa.exec(session).flatMap(a => f(a).exec(session)))

      override def liftIO[A](io: IO[A]): SessionContext[A] =
        SessionContext(Function.const(io))
    }

}