Node fetch url as stream

app.get('/files/:from/:to',  function(req, resp, next) {
  var url1, url2 = "";
  if (req.params.from)url1 = decodeURI(req.params.from);
  if (req.params.to)url2 = decodeURI(req.params.to);
  fetch(url1)
    .then(response => {
      return response.body;  //instance cls=ReadStream
    })