Golang : Set and Get HTTP request headers example

Couple of examples on how to set and get HTTP request headers in Golang.

Example of setting HTTP request header.

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)

Example of getting file download size

 response, err := http.Head(url)
 if err != nil {
 log.Println("Error while downloading", url, ":", err)
 }
 length, _ := strconv.Atoi(response.Header.Get("Content-Length"))
 sourceSize := int64(length)

Example of getting HTTP request header User-Agent information with Header.Get() method

 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)
  }

Apart from User-Agent, here is a list of common HTTP headers :

"accept"

"accept-charset"

"accept-encoding"

"accept-language"

"accept-ranges"

"age"

"access-control-allow-origin"

"allow"

"authorization"

"cache-control"

"content-disposition"

"content-encoding"

"content-language"

"content-length"

"content-location"

"content-range"

"content-type"

"cookie"

"date"

"etag"

"expect"

"expires"

"from"

"host"

"if-match"

"if-modified-since"

"if-none-match"

"if-unmodified-since"

"last-modified"

"link"

"location"

"max-forwards"

"proxy-authenticate"

"proxy-authorization"

"range"

"referrer"

"refresh"

"retry-after"

"server"

"set-cookie"

"strict-transport-security"

"transfer-encoding"

"user-agent"

"vary"

"via"

"www-authenticate"

References :

https://www.socketloop.com/references/golang-net-http-canonicaheaderkey-function-example

https://www.socketloop.com/tutorials/golang-how-to-get-http-request-header-information

https://www.socketloop.com/tutorials/golang-how-to-set-or-add-header-http-responsewriter