snippet from https://amattn.com/p/static_site_generator_using_elixir_and_phoenix.html

generate_html_for_route.ex

def generate_html_for_route(route_path) do
	conn = Phoenix.ConnTest.build_conn()
	conn = get(conn, route_path)
	resp = html_response(conn, 200)

	priv_static_path =
	  Path.join([
		:code.priv_dir(:dash_home),
		"static",
		route_path
	  ])

	assert File.mkdir_p(priv_static_path) == :ok
	priv_static_filepath = Path.join([priv_static_path, "index.html"])

	{:ok, file} = File.open(priv_static_filepath, [:write])
	assert IO.binwrite(file, resp) == :ok
	File.close(file)
end