let GetAllVersions packageName =
  sources
  |> Seq.map (fun source -> async {
      match! getVersionsViaNuGetProtocol1 source packageName,
             getVersionsViaNuGetProtocol2 source packageName,
             getVersionsViaNuGetProtocol3 source packageName,
             getVersionsViaNuGetProtocol4 source packageName with
      | res, ?, ?, ?
      | ?, res, ?, ?
      | ?, ?, res, ?
      | ?, ?, ?, res -> return res })
  |> Async.Parallel
  |> Async.RunSynchronously
  |> Array.choose id
  |> Array.concat