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open System
open System.Threading


let tasks = [
              // job 1 sleeps 5 seconds
              async { printfn "start job 1"

                      // in long running computation without use of Async,
                      // check "myToken.IsCancellationRequested" regularly
                      let! myToken = Async.CancellationToken

                      // Async.Sleep itself cannot be cancelled;
                      // that's why we sleep in small steps in this example;
                      // we don't need to check "myToken.IsCancellationRequested"
                      // in the loop because "do!" inside the async workflow does
                      // that automatically
                      for _ in 1..5 do
                        do! Async.Sleep 1000
                      printfn "end job 1" }

              // job 2 sleeps 10 seconds
              async { printfn "start job 2"
                      for _ in 1..10 do
                        do! Async.Sleep 1000
                      printfn "end job 2" }
            ]

let cts = new CancellationTokenSource()

// start the actual tasks asynchronously (so that we can afterwards start the extra job)
tasks |> Seq.iter (fun task -> Async.Start(task, cts.Token))

// extra job: cancel the actual tasks after 7 seconds
async { printfn "waiting 7 secs until cancel"
        do! Async.Sleep 7000
        cts.Cancel()
        printfn "cancelled"
      }
|> Async.RunSynchronously // start cancel job and wait

printfn "Press enter to end program"
Console.ReadLine() |> ignore