main.go

package main

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"os"

	"golang.org/x/net/html"
	"golang.org/x/net/html/atom"
	"golang.org/x/net/html/charset"
	"golang.org/x/text/transform"
)

func main() {
	root, err := getAndParse("https://www.wikipedia.org/", "")
	if err != nil {
		log.Fatal(err)
	}

	title, ok := getTitle(root)
	if !ok {
		log.Fatal("could not find title")
	}

	html.Render(os.Stdout, title)
	fmt.Println()
}

// getAndParse makes a GET request to the provided URL and attempts
// to parse it as HTML encoded as the given charset. This method
// returns the root node of the page.
//
// If charset is an empty string the charset is guessed.
func getAndParse(url, pageCharset string) (*html.Node, error) {

	// Make a GET request to the provided URL.
	resp, err := http.Get(url)
	if err != nil {
		return nil, fmt.Errorf("GET: %v", err)
	}
	defer resp.Body.Close()

	// html.Parse assumes content to be UTF-8 encoded.
	var reader io.Reader
	if pageCharset == "" {
		// Attempt to guess the charset of the HTML document.
		reader, err = charset.NewReader(resp.Body, "")
		if err != nil {
			return nil, fmt.Errorf("creating new charset reader: %v", err)
		}
	} else {
		// Lookup the charset and attempts to transform it to UTF-8.
		e, name := charset.Lookup(pageCharset)
		if name == "" {
			return nil, fmt.Errorf("provided charset not found")
		}
		reader = transform.NewReader(resp.Body, e.NewDecoder())
	}

	// Use the html package to parse the page.
	root, err := html.Parse(reader)
	if err != nil {
		return nil, fmt.Errorf("parsing HTML: %v", err)
	}
	return root, nil
}

// getTitle recursively looks up the <title> element.
func getTitle(node *html.Node) (*html.Node, bool) {
	if node.DataAtom == atom.Title {
		return node, true
	}
	for c := node.FirstChild; c != nil; c = c.NextSibling {
		if title, ok := getTitle(c); ok {
			return title, true
		}
	}
	return nil, false
}