fsharp-httpclient.fsx

open System.Net.Http
open System.IO

let downloadDataWithHttpClient (url: string) =
    async {
        use hc = new HttpClient()
        // Just read the header
        let! response = hc.GetAsync(url, HttpCompletionOption.ResponseHeadersRead) |> Async.AwaitTask
        // if response.IsSuccessStatusCode
        let filename = Path.GetTempFileName()
        printfn "Starting download to file %s" filename
        let! streamToReadFrom = response.Content.ReadAsStreamAsync() |> Async.AwaitTask
        use streamToWriteTo = File.Open(filename, FileMode.Create)
        do! streamToReadFrom.CopyToAsync(streamToWriteTo) |> Async.AwaitTask
        return ()
    }

let downloadData =
    "http://fsharp.org"
    |> downloadDataWithHttpClient
    |> Async.RunSynchronously