Sequential.scala

object Sequential extends IOApp {

  private val log: Logger[IO] = Slf4jLogger.getLogger[IO].mdc
  
  override def run(args: List[String]): IO[ExitCode] = {
    for {
      _    <- log.info("Start")
      user <- op.withLogContext(_.id("1"))
      _    <- log.info(s"result: $user")
      _    <- log.info("End")
    } yield ExitCode.Success
  }

  private def op: IO[String] = {
    for {
      _      <- log.info("op start")
      result <- opInner.withLogContext(_.tpe("inner"))
      _      <- log.info("op end")
    } yield result
  }

  private def opInner: IO[String] =
    for {
      _      <- log.info("op_inner start")
      result <- IO("user")
      _      <- log.info("op_inner end")
    } yield result
}