Send a file in phoenix (plug)

example_to_download_file.ex

defmodule AppWeb.Controller do
  use AppWeb, :controller
  
  # sending bytes
  def show(conn, %{"id" => id}) do
    data = Storage.get_data_for_file_id(id)

    conn
    |> put_resp_header(
      "content-disposition",
      ~s(attachment; filename="#{id}.jpg")
    )
    |> put_resp_header("content-type", "image/jpeg")
    |> resp(:ok, data)
  end
  
  # sending a file
  def show(conn, %{"id" => id}) do
    conn
    |> put_resp_header(
      "content-disposition",
      ~s(attachment; filename="filename-to-show-to-browser.jpg")
    )
    |> put_resp_header("content-type", "image/jpeg")
    |> send_file(:ok, "path-to-file-on-disk.jpg")
  end
end