How to access Database if function in different module?

I try to atuhorize with jwt, but I get the problem which is when I check email with value email from claims I get the Error 500. That problem because the db is not ready.

This is the code

package route

package route

import (
	"go_fiber/controller"
	"go_fiber/middleware"


	"github.com/gofiber/fiber/v2"
)

func RouteInit(app *fiber.App, userController controller.UserController) {
	app.Get("/users", middleware.AuthMiddleware, userController.FindAll)
	app.Post("/login", userController.Login)
}

package app

package app

import (
	"database/sql"
	"fmt"
	"go_fiber/helper"
	"os"
	"time"

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

func NewDB() *sql.DB {

	var (	
		username = envVariable("DB_USERNAME")
		password = envVariable("DB_PASSWORD")
		host = envVariable("DB_HOST")
		port = envVariable("DB_PORT")
		db_name = envVariable("DB_NAME")
	)

	dns := fmt.Sprintf("%s:%s@tcp(%s:%s)/%s?parseTime=True", username, password, host, port, db_name)

	db, err := sql.Open("mysql", dns)
	if err != nil {
		panic(err)
	}

	db.SetMaxIdleConns(10)
	db.SetMaxOpenConns(100)
	db.SetConnMaxIdleTime(5 * time.Minute)
	db.SetConnMaxLifetime(60 * time.Minute)

	return db
}

package main

package main

import (
	"go_fiber/app"
	"go_fiber/controller"
	"go_fiber/exception"
	"go_fiber/repository"
	"go_fiber/route"
	"go_fiber/service"

	"github.com/go-playground/validator/v10"
	"github.com/gofiber/fiber/v2"
)

func main(){

	var db = app.NewDB()
	app := fiber.New()
	app.Use(func(c *fiber.Ctx) error {
		defer func() {
			if err := recover(); err != nil {
				exception.ErrorHandler(c, err)
			}
		}()
	
		return c.Next()
	})

	validator := validator.New()
	userRepository := repository.NewUserRepository()
    userService := service.NewUserService(userRepository, db, validator)
    userController := controller.NewUserController(userService)
	
	route.RouteInit(app, userController)

	app.Listen(":3000")
}

package middleware

package middleware

import (
	"database/sql"
	"errors"
	"fmt"
	"go_fiber/exception"
	"log"
	"os"
	"time"

	"github.com/gofiber/fiber/v2"
	"github.com/golang-jwt/jwt/v4"
)

func AuthMiddleware(c *fiber.Ctx) error{
	tokenString := c.Cookies("Authorization") 

	log.Printf("(middleware) token : %v", tokenString)

	if tokenString == "" {
		panic(exception.NewUserUnauthorized(errors.New("User Unauthorized").Error()))
	}

	token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method :%v", token.Header["sub"])
		}

		return []byte(os.Getenv("SECRET")), nil
	})

	log.Printf("(middleware) token : %v", token)
	log.Printf("(middleware) error : %v", err)

	if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
		if float64(time.Now().Unix()) > claims["exp"].(float64) {
			panic(exception.NewUserUnauthorized(errors.New("User Unauthorized").Error()))
		}

		log.Printf("(middleware) claims : %v", claims)
		log.Printf("(middleware) ok : %v", ok)
		
		var DB *sql.DB

		tx, err := DB.Begin()
		
		log.Printf("(middleware) tx : %v", tx)
		log.Printf("(middleware) error : %v", err)
		
		query :=`
			SELECT email FROM users 
			WHERE email = ? 
			LIMIT 1
		`
		log.Printf("(middleware) query : %v", query)

		user, err := tx.QueryContext(c.Context(), query, claims["sub"])

		log.Printf("(middleware) user  : %v", user)
		log.Printf("(middleware) error : %v", err)
		

		if err != nil {
			panic(exception.NewUserUnauthorized(errors.New("User Unauthorized").Error()))
		}

		c.Locals("user", user)
		c.Next()
	}else {
		panic(exception.NewUserUnauthorized(errors.New("User Unauthorized").Error()))
	}

	return nil
}

and this part the problem code

var DB *sql.DB
tx, err := DB.Begin()	
log.Printf("(middleware) tx : %v", tx) // No detect in terminal

this the ouput from log

2023/02/12 10:00:04 (middleware) token : eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2NzYxNzEzOTIsInN1YiI6IkphZmFyQGdtYWlsLmNvbSJ9.6nn_IaNACHfe7flFMOXfj1ygZS-U_yrnU_Gvjn8xCp8
2023/02/12 10:00:04 (middleware) token : &{eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2NzYxNzEzOTIsInN1YiI6IkphZmFyQGdtYWlsLmNvbSJ9.6nn_IaNACHfe7flFMOXfj1ygZS-U_yrnU_Gvjn8xCp8 0xc0000a6780 map[alg:HS256 typ:JWT] map[exp:1.676171392e+09 sub:John@gmail.com] 6nn_IaNACHfe7flFMOXfj1ygZS-U_yrnU_Gvjn8xCp8 true}
2023/02/12 10:00:04 (middleware) error : <nil>
2023/02/12 10:00:04 (middleware) claims : map[exp:1.676171392e+09 sub:John@gmail.com]
2023/02/12 10:00:04 (middleware) ok : true

So, How to fix that problem to access db if different package?

You should pass the DB handler down through your route registration to the middleware.

Change your AuthMiddleware so that it is returned by a function that takes db *sql.DB as an argument:

func NewAuthMiddleware(db *sql.DB) fiber.Handler {
    return func(c *fiber.Ctx) error {
       // The rest of your function is here and has access to db
    }
}

You then need to call NewAuthMiddleware in your RouteInit function

func RouteInit(app *fiber.App, userController controller.UserController, db *sql.DB) {
    app.Get("/users", middleware.NewAuthMiddleware(db), userController.FindAll)
    app.Post("/login", userController.Login)
}

Then in your main function pass in the db to RouteInit()

func main() {
    // ... as before

    route.RouteInit(app, userController, db)
}