mongodb connection issue

mongoconnection.go

// GetDatabase connects and returns a new mongodb database (service name is used by default but this can
// be overridden by MongoClientConfig.MongoDatabase)
func GetDatabase(opts ...Option) (*mongo.Database, error) {
	c, err := getConfig(opts...)
	if err != nil {
		return nil, err
	}
	client, err := GetClient(c.conf)
	if err != nil {
		return nil, err
	}

	return client.Database(c.conf.MongoDBDatabase), nil
}

func GetClient(conf *Config) (*mongo.Client, error) {
	if conf == nil {
		return nil, errors.New("conf cannot be empty")
	}
	opts := options.Client()
	opts.ApplyURI(config.MongoDBUri)
	
	log.Println("attempting to connect to mongo")
	ctx, cancel := context.WithTimeout(context.Background(), conf.MongoDBConnectTimeout)
	defer cancel()
	client, err := mongo.Connect(ctx, opts)
	if err != nil {
		log.Println("connection failed")
		return nil, err
	}
	log.Println("successfully connected to mongo")

	// Ping to make sure connection is usable
	log.Println("attempting ping")
	ctx, cancel = context.WithTimeout(context.Background(), conf.MongoDBConnectTimeout)
	defer cancel()
	if err := client.Ping(ctx, nil); err != nil {
		log.Println("ping failed")
		return nil, err
	}

	return client, err
}

persistence.go

func (s service) GetAllMMs(ctx context.Context, filter map[string]interface{}) ([]matchmaking.MM, error) {
	var mms []matchmaking.MM
	cursor, err := s.db.Collection(mmCol).Find(ctx, filter)
	if err != nil {
		return mms, err
	}

	defer cursor.Close(ctx)

	for cursor.Next(ctx) {
		var mm matchmaking.MM
		if err := cursor.Decode(&mm); err != nil {
			s.log.WithError(err).Error("could not unmarshal returned document into a matchmaking")
			return mms, err
		}
		mms = append(mms, mm)
	}

	if len(mms) == 0 {
		return mms, util.NewNotFoundError(filter)
	}

	return mms, nil
}