How to create a photo gallery in Go?

Photo gallery is a way of displaying the different images that are saved at a specific location. Here the different images are uploaded by user in a specified folder. For displaying the images first of all we need to read the directory containing the different images, and there after reading display the images one by one.

main.go

package main

import (
	"crypto/sha1"
	"fmt"
	"html/template"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
)

var tpl *template.Template

func init() {
	tpl = template.Must(template.ParseGlob("templates/*"))
}

func main() {
	http.HandleFunc("/", index)
	http.Handle("/gallery/", http.StripPrefix("/gallery", http.FileServer(http.Dir("./gallery"))))
	http.Handle("/favicon.ico", http.NotFoundHandler())
	http.ListenAndServe(":8080", nil)
}

func index(w http.ResponseWriter, req *http.Request) {
	if req.Method == http.MethodPost {
		mf, fh, err := req.FormFile("nf")
		if err != nil {
			fmt.Println(err)
		}
		defer mf.Close()
		// create sha for file name
		ext := strings.Split(fh.Filename, ".")[1]
		h := sha1.New()
		io.Copy(h, mf)
		fname := fmt.Sprintf("%x", h.Sum(nil)) + "." + ext
		// create new file
		wd, err := os.Getwd()
		if err != nil {
			fmt.Println(err)
		}
		path := filepath.Join(wd, "gallery", fname)
		nf, err := os.Create(path)
		if err != nil {
			fmt.Println(err)
		}
		defer nf.Close()
		mf.Seek(0, 0)
		io.Copy(nf, mf)
	}

	file, err := os.Open("gallery")
	if err != nil {
		log.Fatalf("failed opening directory: %s", err)
	}
	defer file.Close()

	list, _ := file.Readdirnames(0) // 0 to read all files and folders
	tpl.ExecuteTemplate(w, "index.gohtml", list)
}

index.html

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Image Uploader</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
    <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
  </head>
  <body>
    <div class="container">
      <h1>Photo Gallery</h1>
      <hr class="mt-2 mb-5">
      <div class="row text-center text-lg-left">
        {{range .}}
        <div class="col-lg-3 col-md-4 col-6">
          <a href="#" class="d-block mb-4 h-100">
          <img class="img-fluid img-thumbnail" src="/gallery/{{.}}">
          </a>
        </div>
        {{end}}
      </div>
      <hr class="mt-2 mb-5">
      <div class="row">
        <div class="col-lg-3 col-md-4 col-6">
          <form method="post" enctype="multipart/form-data">
            <div class="input-group">
              <div class="input-group-prepend">
                <span class="input-group-text" id="inputGroupFileAddon01">Upload</span>
              </div>
              <div class="custom-file">
                <input type="file" class="custom-file-input" name="nf" aria-describedby="inputGroupFileAddon01" id="inputGroupFile01" required> 
                <label class="custom-file-label" for="inputGroupFile01">Choose file</label>	
              </div>
            </div>
            <div class="input-group">
              <div class="custom-file">
                <input type="submit" class="btn btn-primary">
              </div>
            </div>
          </form>
        </div>
      </div>
    </div>
  </body>
</html>

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How to create a photo gallery in Go?

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