Gorm Can't Insert Value into Sqlite - database

Question

I use dao layer to init sqlitedb and try to insert a col into db in main.go
The Problem is When the main.go is finish and the database is created.But No any data in db..
my model.go is here
package model
import "gorm.io/gorm"
type User struct {
gorm.Model
Username string `json:"username"`
Password string `json:"password"`
}
and my gorm dao.go is here
package dao
import (
"go_blog/model"
"log"
"gorm.io/driver/sqlite"
"gorm.io/gorm"
)
type Manager interface {
AddUser(user *model.User)
}
type manager struct {
db *gorm.DB
}
var Mgr Manager
func init() {
db, err := gorm.Open(sqlite.Open("database/blog.db"), &gorm.Config{})
if err != nil {
log.Fatal("Failed to INIT db:", err)
}
Mgr = &manager{db: db}
db.AutoMigrate(&model.User{})
log.Fatal("Init DB Successful")
}
func (mgr *manager) AddUser(user *model.User) {
mgr.db.Create(user)
}
when I use main.go to run the Mgr.AddUser function,I look into sqlite db,but the DB is no any data in there...So Confuse..
main.go is here
package main
import (
"go_blog/dao"
"go_blog/model"
)
func main() {
user := model.User{
Username: "tom",
Password: "123",
}
dao.Mgr.AddUser(&user)
}