build.sbt

name := "scalaScratch"

scalaVersion := "2.12.6"

version := "0.1"

scalacOptions := Seq(
  "-Ypartial-unification",
  "-deprecation",
  "-feature",
  "-unchecked",
  "-language:higherKinds",
  "-Xlog-reflective-calls",
  "-Yinfer-argument-types"
)


def catsVersion       = "1.1.0"

def catsEffectVersion = "1.0.0-RC2"
// def catsEffectVersion = "1.0.0-RC2-93ac33d"
// def monixVersion      = "3.0.0-RC1"
// def fs2Version        = "0.10.1"
def fs2Version        = "1.0.0-M1"


libraryDependencies ++= Seq(
  // "io.monix" %% "monix" % monixVersion,

  "org.typelevel" %% "cats-core"   % catsVersion,
  "org.typelevel" %% "cats-effect" % catsEffectVersion,

  "co.fs2" %% "fs2-core" % fs2Version,
  "co.fs2" %% "fs2-io"   % fs2Version
)

main.scala

package scratch

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration._

import cats.effect.IO


object Main {

  def timeoutLeak() {

    val p = IO.pure(())
    val to = IO.sleep(100.seconds)

    // racing with r10 instead of to actually doesn't make thing worse
    /*
     val r1 = IO.race(to, to)
     val r2 = IO.race(r1, r1)
     val r3 = IO.race(r2, r2)
     val r4 = IO.race(r3, r3)
     val r5 = IO.race(r4, r4)
     val r6 = IO.race(r5, r5)
     val r7 = IO.race(r6, r6)
     val r8 = IO.race(r7, r7)
     val r9 = IO.race(r8, r8)
     val r10 = IO.race(r9, r9)
     */

    def loop(): IO[Unit] = {
      IO.race(to, p)
        .flatMap(_ => loop())
    }

    (
      for {
        fib1 <- loop().start
        fib2 <- loop().start
        fib3 <- loop().start
        fib4 <- loop().start

        _ <- fib1.join
        _ <- fib2.join
        _ <- fib3.join
        _ <- fib4.join
      } yield {
        ()
      }
    )
      .unsafeRunSync
  }

    def main(args: Array[String]) {
      timeoutLeak()
    }
}