Golang script to rapidly insert data into a MySQL database

insert.go

package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"
	"sync"
	// "math/rand"
	"unicode/utf8"

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

type Item struct {
	ID           string   `json:"id"`
	Shop         string   `json:"shop"`
	Country      string   `json:"country"`
	Location     string   `json:"location"`
	DownloadedOn int      `json:"downloaded_on"`
	Language     string   `json:"language"`
	Name         string   `json:"name"`
	Brand        string   `json:"brand"`
	Eans         []string `json:"eans"`
	Categories   []string `json:"categories"`
	Nutriscore   string   `json:"nutriscore"`
	Prices       []Prices `json:"prices"`
}
type Prices struct {
	Regular float64 `json:"regular"`
	Promo   float64 `json:"promo"`
	Unit    string  `json:"unit"`
}

var (
	glob_items []string
	lock       sync.Mutex
)

func main() {
	glob_items = GetItems()
	for i := 0; i <= 100; i++ {
		go Inserter(i)
	}

	wg := sync.WaitGroup{}
	wg.Add(1)
	wg.Wait()
}

func GetItems() []string {
	var items []string

	folder := "data"
	files, _ := ioutil.ReadDir(folder)
	for _, file := range files {
		jsonFile, err := os.Open("data/" + file.Name())
		if err != nil {
			panic(err)
		}

		scanner := bufio.NewScanner(jsonFile)
		for scanner.Scan() {
			items = append(items, scanner.Text())
		}

		jsonFile.Close()
		fmt.Printf("Collecting items from JSON files: %v\n", len(items))
	}

	return items
}

func GetItem() (item string, empty bool) {
	lock.Lock()
	if len(glob_items) > 0 {
		item, glob_items = glob_items[len(glob_items)-1], glob_items[:len(glob_items)-1]
		lock.Unlock()
		fmt.Println(len(glob_items))
		return item, false
	}

	lock.Unlock()
	return item, true
}

func Inserter(goroutine int) {
	db, err := sql.Open("mysql", "USER:PASSWORD@tcp(HOST)/DATABASE")
	defer db.Close()
	if err != nil {
		panic(err)
	}

	var empty bool
	var itemstring string

	for {
		itemstring, empty = GetItem()
		if empty {
			break
		}

		var item Item

		if !utf8.ValidString(itemstring) {
			fmt.Println("Something wrong with utf8 encoding!")
			fmt.Println(itemstring)
			continue
		} else {
			json.Unmarshal([]byte(itemstring), &item)
		}

		q := "INSERT INTO `products` (downloaded_on, shop_id, shop, country, location, language, name, brand, nutriscore) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?);"
		insert, err := db.Prepare(q)
		if err != nil {
			fmt.Println(err)
		}

		resp, err := insert.Exec(item.DownloadedOn, item.ID, item.Shop, item.Country, item.Location, item.Language, item.Name, item.Brand, item.Nutriscore)
		insert.Close()

		if err != nil {
			fmt.Println(err)
		}

		lastInsertId, err := resp.LastInsertId()
		if lastInsertId == 0 {
			continue
		}
		if err != nil {
			fmt.Println(item)
			fmt.Println(err)
			return
		}

		for _, ean := range item.Eans {
			q := "INSERT INTO `eans` (product_id, ean) VALUES (?, ?);"
			insert, _ := db.Prepare(q)
			_, err = insert.Exec(lastInsertId, ean)
			insert.Close()
		}

		for _, category := range item.Categories {
			q := "INSERT INTO `categories` (product_id, category) VALUES (?, ?)"
			insert, err := db.Prepare(q)
			if err != nil {
				fmt.Println(err)
			}
			_, err = insert.Exec(lastInsertId, category)
			insert.Close()
			if err != nil {
				fmt.Println(err)
			}
		}

		for _, prices := range item.Prices {
			q := "INSERT INTO `prices` (product_id, regular, promo, unit) VALUES (?, ?, ?, ?)"
			insert, _ := db.Prepare(q)
			_, err = insert.Exec(lastInsertId, prices.Regular, prices.Promo, prices.Unit)
			insert.Close()
		}
	}
}