A simple Go utility for work, where we need to get the version of a site through its generator meta tag

version.go

package main

import (
	"bufio"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"regexp"
	"strconv"
)

// Site type holds information about sites
type Site struct {
	name, url string
}

var sites = []Site{
	{"Example 1", "example-site.com"},
	{"Example 2", "example-site-2.com"},
	{"Example 3", "example-site-3.com"},
}

// Parser type holds information about the parsing
type Parser struct {
	url, body string
}

func (p *Parser) setURL(url string) {
	p.url = url
	p.body = ""
}

func (p *Parser) getMatches(regexString string, index int) string {
	regex, _ := regexp.Compile(regexString)

	matches := regex.FindStringSubmatch(p.body)
	if len(matches) == index+1 {
		return matches[index]
	}

	return "N/A"
}

func (p *Parser) getPage() {
	if len(p.url) > 5 && p.url[:4] != "http" {
		p.url = "http://" + p.url
	}

	res, err := http.Get(p.url)
	if err != nil {
		fmt.Println("\nError: Could not fetch " + p.url)
		return
	}

	body, err := ioutil.ReadAll(res.Body)
	res.Body.Close()
	if err != nil {
		fmt.Println("\nError: Could not parse page")
		fmt.Println(err)
		return
	}

	p.body = string(body)

	title := p.getMatches("(<title>)([^<]+)", 2)
	version := p.getMatches("(<meta name=\"generator\" content=\")([^\"]+)", 2)

	fmt.Printf("\n%10s : %s\n", "URL", p.url)
	fmt.Printf("%10s : %s\n", "Title", title)
	fmt.Printf("%10s : %s\n\n", "Version", version)
}

func getInput() {
	reader := bufio.NewReader(os.Stdin)
	parser := Parser{}

	for {
		for index, site := range sites {
			fmt.Printf("[%02d] %-18s  ", index, site.name)
			if index%3 == 2 {
				fmt.Println("")
			}
		}
		fmt.Print("\n\nEnter selection, a URL, or q/quit/exit to quit: ")
		userInput, _ := reader.ReadString('\n')
		if userInput == "exit\n" || userInput == "quit\n" || userInput == "q\n" {
			return
		}

		userInput = userInput[:len(userInput)-1]
		if num, err := strconv.Atoi(userInput); err == nil && num < len(sites) {
			parser.setURL(sites[num].url)
			parser.getPage()
		} else if userInput != "" {
			parser.setURL(userInput)
			parser.getPage()
		}
	}
}

func main() {
	if len(os.Args) > 1 {
		parser := Parser{url: os.Args[1]}
		parser.getPage()
	} else {
		getInput()
	}
}