Is this safe?

IsThisSafe.scala

def call(): Future[String] = ???

val strings = Var.async[Try[String]](None) { strings =>
  def loop(): Future[Unit] =
    call().transform {
      case Return(s) =>
        strings() = Return(s)
        Future.sleep(1.minute).before(loop())
      case Throw(NonFatal(e)) =>
        strings() = Throw(e)
        Future.sleep(1.minute).before(loop())
      case Throw(e) =>
        strings() = Throw(e)
    }
  
  val working = loop()
  Closable.make { deadline =>
    working.raise(Cancelled)
    Future.Unit
  }
}