Golang : Get curl -I or head data from URL example

Problem :

Need a way to make a HEAD request from URL and extract a few fields of header data from the response.

Solution :

A HEAD request is similar to curl -I command and in Golang, the similar task can be achieved with the net/http.Head() function.

Here is an example of HEAD request in Golang :

 package main

 import (
 "fmt"
 "net/http"
 )

 func main() {
 resp, err := http.Head("http://www.golang.org")

 if err != nil {
 fmt.Println(err)
 return
 }

 fmt.Println(resp)
 // you can isolate the data further
 // READ http://golang.org/pkg/net/http/#Response 

 contentLength := resp.ContentLength
 fmt.Println("Content Length : ", contentLength)
 }

and the output :

&{200 OK 200 HTTP/1.1 1 1 map[Content-Type:[text/html; charset=utf-8] Date:[Mon, 20 Jul 2015 09:02:28 GMT] Server:[Google Frontend]

Content-Length:[7537] Alternate-Protocol:[80:quic,p=0]] 0xc208054500 7537 [] false map[] 0xc208032750 }

Content Length : 7537

and compare the output to curl -I command.

>curl -I https://www.golang.org

HTTP/1.1 200 OK

Content-Type: text/html; charset=utf-8

Date: Mon, 20 Jul 2015 08:54:37 GMT

Server: Google Frontend

Content-Length: 7537

Alternate-Protocol: 443:quic,p=1

References :

http://golang.org/pkg/net/http/#Head

http://golang.org/pkg/net/http/#Response