将文件从Golang后端流传输到Node前端

I have set up a backend on Golang (wrapped in Gin gonic framework) and the frontend is run on NodeJS (wrapped in Express framework). Assume Express is to make a request to Golang backend to request a file, receive it back to Express and push to the client.

Frontend Node:

var request = require('request');

router.get('/testfile', function (req, res, next) {

  // URL to Golang backend server
  var filepath = 'http://127.0.0.1:8000/testfile';

  request(filepath, function (error, response, body) {

    // This is incorrect, as it's just rendering the body to the client as text
    res.send(body);  

  })

});

Backend Golang:

r.GET("/testfile", func(c *gin.Context) {

    url := "http://upload.wikimedia.org/wikipedia/en/b/bc/Wiki.png"

    timeout := time.Duration(5) * time.Second
    transport := &http.Transport{
        ResponseHeaderTimeout: timeout,
        Dial: func(network, addr string) (net.Conn, error) {
            return net.DialTimeout(network, addr, timeout)
        },
        DisableKeepAlives: true,
    }
    client := &http.Client{
        Transport: transport,
    }
    resp, err := client.Get(url)
    if err != nil {
        fmt.Println(err)
    }
    defer resp.Body.Close()

    c.Writer.Header().Set("Content-Disposition", "attachment; filename=Wiki.png")
    c.Writer.Header().Set("Content-Type", c.Request.Header.Get("Content-Type"))
    c.Writer.Header().Set("Content-Length", c.Request.Header.Get("Content-Length"))

    //stream the body to the client without fully loading it into memory
    io.Copy(c.Writer, resp.Body)

})

My question is: How do I properly request a file from Node to Golang, and render it back to the client, keeping the possibility of streaming file (if there would be a large file)?