print http header from go

print_header.go

package main

import (
	"errors"
	"flag"
	"fmt"
	"net/http"
)

func main() {
	url := flag.String("url", "http://www.yahoo.co.jp/", "get header url. default is http://www.yahoo.co.jp/")
	r := flag.Bool("r", false, "if it is true, do the redirect.")
	flag.Parse()

	c := new(http.Client)
	if !*r {
		c.CheckRedirect = func(req *http.Request, via []*http.Request) error { return errors.New("not redirect") }
	}

	resp, err := c.Get(*url)
	if err != nil {
		fmt.Println("error: ", err)
	} else {
		defer resp.Body.Close()
		for k, v := range resp.Header {
			fmt.Println("header key: ", k)
			for _, value := range v {
				fmt.Println("\theader value: ", value)
			}
		}
	}
}

result

$ go run print_header.go 
header key:  Server
	header value:  nginx
header key:  Date
	header value:  Thu, 13 Aug 2015 17:38:26 GMT
header key:  Content-Type
	header value:  text/html; charset=UTF-8
header key:  P3p
	header value:  policyref="http://privacy.yahoo.co.jp/w3c/p3p_jp.xml", CP="CAO DSP COR CUR ADM DEV TAI PSA PSD IVAi IVDi CONi TELo OTPi OUR DELi SAMi OTRi UNRi PUBi IND PHY ONL UNI PUR FIN COM NAV INT DEM CNT STA POL HEA PRE GOV"
header key:  Cache-Control
	header value:  private, no-cache, no-store, must-revalidate
header key:  Vary
	header value:  Accept-Encoding
header key:  Expires
	header value:  -1
header key:  Pragma
	header value:  no-cache
header key:  X-Xrds-Location
	header value:  https://open.login.yahooapis.jp/openid20/www.yahoo.co.jp/xrds
header key:  X-Frame-Options
	header value:  SAMEORIGIN