Golang : Get and Set User-Agent examples

Problem :

You want to detect User-Agent of your web application users and also setup your own User-Agent name for your Golang application.

How to get and set User-Agent in Golang application?

Solution :

Example 1 :

 package main

 import (
 "fmt"
 "net/http"
 )

 func getUserAgent(w http.ResponseWriter, r *http.Request) {
 ua := r.Header.Get("User-Agent")
 fmt.Printf("user agent is: %s \n", ua)
 w.Write([]byte("user agent is " + ua))
 }

 func main() {
 http.HandleFunc("/", getUserAgent)
 http.ListenAndServe(":8080", nil)
 }

Example 2:

 package main

 import (
 "fmt"
 "net/http"
 )

 func getUserAgent(w http.ResponseWriter, r *http.Request) {
 ua := r.UserAgent() //<---- simpler and faster!
 fmt.Printf("user agent is: %s \n", ua)
 w.Write([]byte("user agent is " + ua))
 }

 func main() {
 http.HandleFunc("/", getUserAgent)
 http.ListenAndServe(":8080", nil)
 }

To set User-Agent for your Golang application, first create a client and set client's request header with [your user-agent name] before executing the request.

For instance :

 client := &http.Client{}
 request, err := http.NewRequest("GET", "http://example.com", nil)

 if err != nil {
 log.Fatalln(err)
 }
 request.Header.Set("User-Agent", "[your user-agent name]")
 resp, err := client.Do(req)

The web site example.com will detect your program User-Agent as whatever name you choose for [your user-agent name].

Reference :

https://www.socketloop.com/references/golang-net-http-request-useragent-and-referer-functions-example