A simple reverse proxy example in Go

This example shows you a Go HTTP Server that forwards requests to an upstream Server using a HTTP client. Note that this example does not stream the upstream server’s responses but downloads them to RAM and then serves them to the client (hence you might need to improve upon this example if you intend to serve large files).

Also, note that this example does not implement proper error handling for the upstream request since it’s only intended to serve as a basic starting point for you to develop your own reverse proxy implementation.

package main

import (
    "fmt"
    "io/ioutil"
    "log"
    "net/http"
)

func main() {
    client := &http.Client{}
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        // Perform request
        url := "https://techoverflow.net" + r.URL.Path
        req, _ := http.NewRequest(r.Method, url, r.Body)
        req.Header = r.Header
        resp, _ := client.Do(req)
        // Cleanup when this function ends
        defer resp.Body.Close()
        // Copy headers from request to response
        header := w.Header()
        for name, headers := range resp.Header {
            // Iterate all headers with one name (e.g. Content-Type)
            for _, hdr := range headers {
                header.Add(name, hdr)
            }
        }
        // Read all the response data into a []byte
        body, _ := ioutil.ReadAll(resp.Body)
        // Write header & body
        w.WriteHeader(resp.StatusCode)
        w.Write(body)
    })
    // log.Fatal shows you if there is an error like the
    //  port already being used
    fmt.Println("Listening on port 8080")
    log.Fatal(http.ListenAndServe(":8080", nil))
}

Further reading:

• Go net/http package
• Iterating HTTP client response headers in Go (which we use as a basis to implement our header copying mechanism)