HttpClient.Timeout does not seem to be working

Question

The small test app tries to communicate with the server using HttpClient, with the Timeout specified.

But it looks like the timeout never aborts the client request:

#r "System.Core.dll"
#r "System.Net.dll"
#r "System.Net.Http.dll"
#r "System.Web.dll"
#r "System.Web.Http.dll"

open System
open System.Net
open System.Net.Http
open System.Threading
open System.Web
open System.Web.Http

let listener = new HttpListener()

// https://stackoverflow.com/questions/4019466/httplistener-access-denied/4115328#4115328
// netsh http add urlacl url=http://*:7842/ user=COMPUTER\User
// netsh http show urlacl                   - make sure that it exists
// netsh http delete urlacl http://*:7842/ - delete it
listener.Prefixes.Add("http://*:7842/")
listener.Start()

let handler = async {
    while true do
        let context = listener.GetContext()
        Console.WriteLine("ok")
}

let requester = async {
    let client = new HttpClient()
    client.Timeout <- TimeSpan.FromMilliseconds(float(1))
    client.BaseAddress <- Uri("http://127.0.0.1:7842/")
    try
        let! result = client.GetAsync("") |> Async.AwaitTask
        printf "result: %s" (string(result))
    with
    | _ -> printf "timeout?"
}

Async.Start(handler)
Thread.Sleep(750)
Async.Start(requester)

Thread.Sleep(100000)

The timeout never happen in this app which is very strange.

Update: It may be related to HttpClient.GetAsync(...) never returns when using await/async

Update2: It seems that this workaround is working but not sure if it correct:

try
    let requestTask = client.GetAsync("")
    let! success = Async.AwaitIAsyncResult(requestTask, 3000)
    let result = requestTask.Result

    printf "result: %s" (string(result))
with
| ex -> printf "timeout? %s\n" (ex.ToString())

Should the client be Disposed (probably not as it can be reused for another requests in other threads/tasks)?