Dynamically returns a zip file consisting of multiple Amazon S3 objects

gistfile1.go

// download zipfile
func ZipHandler(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	token := vars["token"]

	db, err := sql.Open("mysql", config.DSN)
	if err != nil {
		panic(err.Error()) // Just for example purpose. You should use proper error handling instead of panic
	}

	defer db.Close()

	var d delivery

	{
		stmt, err := db.Prepare("SELECT deliveryid FROM deliveries WHERE (token = ?)")

		if err != nil {
			log.Fatal(err)
		}

		if err := stmt.QueryRow(token).Scan(&d.deliveryid); err != nil {
			// log.Fatal(err)
			http.NotFound(w, r)
			return
		}

		stmt.Close()
	}

	filename := fmt.Sprintf("%s.zip", token)

	w.Header().Set("Content-Type", "application/zip")
	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))

	{
		zw := zip.NewWriter(w)

		auth := aws.Auth{config.AWS_ACCESS_KEY, config.AWS_SECRET_KEY}

		// make region variable and save in database
		conn := s3.New(auth, aws.Regions["eu-west-1"])
		b := conn.Bucket(config.BUCKET)

		stmt, err := db.Prepare("SELECT attachmentid, url, filename, size, filetype FROM attachments WHERE (token = ?)")
		rows, err := stmt.Query(token)

		if err != nil {
			log.Fatal(err)
		}

		for rows.Next() {
			var a attachment

			if err := rows.Scan(&a.attachmentid, &a.url, &a.filename, &a.size, &a.filetype); err != nil {
				log.Fatal(err)
				continue
			}

			fi, err := b.GetReader(a.url)

			if err != nil {
				// log.Info(err)
				continue
			}

			header := &zip.FileHeader{
				Name:         a.filename,
				Method:       zip.Store,
				ModifiedTime: uint16(time.Now().UnixNano()),
				ModifiedDate: uint16(time.Now().UnixNano()),
			}

			fw, err := zw.CreateHeader(header)

			if err != nil {
				log.Fatal(err)
			}

			if _, err = io.Copy(fw, fi); err != nil {
				log.Fatal(err)
			}

			if err = fi.Close(); err != nil {
				log.Fatal(err)
			}
		}

		stmt.Close()

		if err := zw.Close(); err != nil {
			log.Fatal(err)
		}
	}

	return
}