You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: http_request_change_headers.go
    path of file: ./repos/Cookbook/go/web_scraping/set_user_agent
    
    the code of the file until where you have to start completion: // http_request_change_headers.go
package main

import (
	"io"
	"log"
	"net/http"
	"os"
	"time"
)

func main() {
	// Create HTTP client with timeout
	client := &http.Client{
		Timeout: 30 * time.Second,
	}

	// Create and modify HTTP request before sending
	request, err := http.NewRequest("GET", "https://www.devdungeon.com", nil)
	if err != nil {
		log.Fatal(err)
	}
	request.Header.Set("User-Agent", "Not Firefox")

	// Make request
	resp
    
func main() {
	// Create HTTP client with timeout
	client := &http.Client{
		Timeout: 30 * time.Second,
	}

	// Create and modify HTTP request before sending
	request, err := http.NewRequest("GET", "https://www.devdungeon.com", nil)
	if err != nil {
		log.Fatal(err)
	}
	request.Header.Set("User-Agent", "Not Firefox")

	// Make request
	response, err := client.Do(request)
	if err != nil {
		log.Fatal(err)
	}
	defer response.Body.Close()

	// Copy data from the response to standard output
	_, err = io.Copy(os.Stdout, response.Body)
	if err != nil {
		log.Fatal(err)
	}
}