Using cats-effect's MapRef, simple

SimpleMapRef.scala

//> using scala 3.3
//> using dep org.typelevel::cats-effect:3.5.4

import cats.effect.{IO, IOApp}
import cats.effect.std.MapRef

object SimpleMapRef extends IOApp.Simple:
  
  private val simpleSample =
    for
      mr <- MapRef.ofSingleImmutableMap[IO, Int, String]()
      _ <- mr.setKeyValue(1, "one")
      _ <- mr(1).get.flatMap:
        case None => IO.raiseError(new NoSuchElementException("Not found value for key 1, this is actually impossible"))
        case Some(v) => IO.println(s"Found value $v for key 1")
    yield ()

  override val run = simpleSample