Async workflow to start something and come back to it later

LongAsyncTask

let now () = System.DateTime.Now

let someOtherWork times = async {
    let rec inner' times current = async {
        if times = current then
            printfn "someOtherWork FINISHED"
        else
            do! Async.Sleep 1000
            let next = current + 1
            printfn "someOtherWork step %d @ %s" next (now() |> string)
            do! inner' times next
    }
    printfn "someOtherWork STARTED"
    do! inner' times 0
}

// Async task that should start while we do other work.
// unit -> Async<string>
let childAsync () =
    async {
        do! Async.Sleep(5000)
        return now()
    }

// Async task to start the child and return a reference to it.
// Returns Async<Async<string>>
let returnAsync () =
    async {
        now()
        |> string
        |> printfn "LONG TASK STARTED @ %s"
        //Async.StartChild returns Async<Async<T>>
        // let! blocks on an async.
        // a is Async<T> (T is a string)
        let! a = childAsync() |> Async.StartChild
        return a // returns Async<string>
    } // whole async returns Async<Async<string>

// RunSynchronously unwraps Aysnc<T>
// Async<Async<T>> -> Async<T>
let longTask = returnAsync() |> Async.RunSynchronously

someOtherWork 10 |> Async.Start

longTask
|> Async.RunSynchronously
|> string
|> printfn "LONG TASK ENDED: %s"