```golang
package main

import (
	"fmt"
	"log"
	"os"
	"strconv"
	"time"
	"io/ioutil"

	_ "github.com/go-sql-driver/mysql"
	"github.com/jmoiron/sqlx"
)

var (
	db *sqlx.DB
)

type Post struct {
	ID           int       `db:"id"`
	UserID       int       `db:"user_id"`
	Imgdata      []byte    `db:"imgdata"`
	Body         string    `db:"body"`
	Mime         string    `db:"mime"`
	CreatedAt    time.Time `db:"created_at"`
	CommentCount int
	CSRFToken    string
}

func main() {
	host := os.Getenv("ISUCONP_DB_HOST")
	if host == "" {
		host = "localhost"
	}
	port := os.Getenv("ISUCONP_DB_PORT")
	if port == "" {
		port = "3306"
	}
	_, err := strconv.Atoi(port)
	if err != nil {
		log.Fatalf("Failed to read DB port number from an environment variable ISUCONP_DB_PORT.\nError: %s", err.Error())
	}
	user := os.Getenv("ISUCONP_DB_USER")
	if user == "" {
		user = "root"
	}
	password := os.Getenv("ISUCONP_DB_PASSWORD")
	dbname := os.Getenv("ISUCONP_DB_NAME")
	if dbname == "" {
		dbname = "isuconp"
	}

	dsn := fmt.Sprintf(
		"%s:%s@tcp(%s:%s)/%s?charset=utf8mb4&parseTime=true&loc=Local",
		user,
		password,
		host,
		port,
		dbname,
	)

	db, err = sqlx.Open("mysql", dsn)
	if err != nil {
		log.Fatalf("Failed to connect to DB: %s.", err.Error())
	}
	defer db.Close()

	post := Post{}
	sum := 10036
	var filename = ""
	for i := 0; i < sum; i++ {
		fmt.Println("%d:", i)
		derr := db.Get(&post, "SELECT `id`, `user_id`, `mime`, `imgdata`, `body`, `created_at` FROM `posts` WHERE `id` = ?", i)
		if derr != nil {
			fmt.Println(derr.Error())
			continue
		}
		if post.Mime == "image/jpeg" {
			filename = fmt.Sprintf("%d.jpg", i)
		} else if post.Mime == "image/png" {
			filename = fmt.Sprintf("%d.png", i)
		} else if post.Mime == "image/gif" {
			filename = fmt.Sprintf("%d.gif", i)
		} else {
			continue;
		}
		fmt.Println("%s", filename)
		//fmt.Println("%s", post.Body)
		ioutil.WriteFile(filename, post.Imgdata, 0644)
		// w.Header().Set("Content-Type", post.Mime)
		//fmt.Println(filename)
		// _, err := w.filename);
		// if err != nil {
		// 	fmt.Println(err.Error())
		// }
	}

}


```