If can , Do you have example project , I really need to learn and use it with production. thx in advance
Have you read the Quickstart?
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Sample code that I used many times… Feel free to use it. It is just a draft, it could be not valid as I don’t have a machine with go installed with me today 
// Use interface (cleaner)
type DbStore interface {
GetDb() *mongo.Database
GetClient() (*mongo.Client, error)
Coll(name string, opts ...*options.CollectionOptions) *mongo.Collection
Disconnect() error
}
type dbStore struct {
db *mongo.Database
client *mongo.Client
}
func NewDbStore(opts *options.ClientOptions, dbName string) (DbStore, error) {
client, db, err := connect(opts, dbName)
if err != nil {
return nil, err
}
return &dbStore{db: db, Client: client}, nil
}
func (md *dbStore) GetDb() *mongo.Database {
return md.db
}
func (md *dbStore) GetClient() (*mongo.Client, error) {
if md.client != nil {
return md.client, nil
}
return nil, errors.New("client is missing (nil) in Mongo Data Store")
}
func (md *dbStore) Coll(name string, opts ...*options.CollectionOptions) Collection {
return NewCollection(md.db, name, opts...)
}
func (md *dbStore) Disconnect() error {
err := md.client.Disconnect(ctx())
if err != nil {
return err
}
return nil
}
func connect(opts *options.ClientOptions, dbName string) (*mongo.Client, *mongo.Database, error) {
var connectOnce sync.Once
var db *mongo.Database
var client *mongo.Client
var err error
connectOnce.Do(func() {
client, db, err = connectToMongo(opts, dbName)
})
return client, db, err
}
func connectToMongo(opts *options.ClientOptions, dbName string) (*mongo.Client, *mongo.Database, error) {
var err error
client, err := mongo.NewClient(opts)
if err != nil {
return nil, nil, err
}
ctx, cancel := context.WithTimeout(context.Background(), defaultConfig.ctxTimeout)
defer cancel()
err = client.Connect(ctx)
if err != nil {
return nil, nil, err
}
err = client.Ping(ctx, readpref.Primary())
if err != nil {
_ = client.Disconnect(ctx)
return nil, nil, errors.New(fmt.Sprintf("Cannot connect do db. Error: %v", err))
}
var db = client.Database(dbName)
return client, db, nil
}
A simple repo
type MyRepo interface{
Find(ctx context.Context, filters interface{}) []SomeType, error
}
type myRepo struct {
store DbStore
}
func NewMyRepo(store DbStore) MyRepo {
return myRepo{ store: store }
}
func (r *myRepo) Find(ctx context.Context , filters interface{}) []Document, error{
// Query
}
Some file (like main.go or any init file that runs on startup)
var mystore DbStore
var myRepo MyRepo
func main() {
mystore = NewDbStore(yourOptions, "yourDbName")
myRepo = NewMyRepo(mystore)
}
in any file
myRepo.Find(ctx, filter)
Or if you want something more straightforward
import (
"context"
"time"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
"go.mongodb.org/mongo-driver/mongo/readpref"
)
// Global var
var client *mongo.Client
func main() {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb://localhost:27017"))
}
In some file
func PerformSomethingWithClient() {
client.XXXXX()
}