How to return value from Task.async?

gistfile1.exs

defmodule Test do

    @doc ~S"""
      iex> Test.download("http://www.six-swiss-exchange.com/data/market/statistics/corrections_2017-02-03.csv", "test.csv")
    """ 
    def download(src, output_filename) do
        Logger.info "Downloading #{src} -> #{output_filename}"
        Task.async(getURL(src))
        |> Task.await
        |> Task.async(&(fn -> File.write!(output_filename, &1) end))
        |> Task.await
        Logger.info("Done Downloading #{src} -> #{output_filename}")
      end

      defp getURL(src) do 
        case HTTPoison.get(src) do
          {:ok, response} -> response.body
          {:error, error} -> (
            Logger.error "could not download file. #{error.id} - #{error.reason}"
            :error
          )
        end
      end
end

@soriyath Could you explain your exact goal in this gist?