(OraklNode) Consideration for singleton pattern implementation

[nick-bisonai]

func getPool(ctx context.Context, once *sync.Once) (*pgxpool.Pool, error) {
	var err error

	connectionString := loadPgsqlConnectionString()
	if connectionString == "" {
		err = errors.New("DATABASE_URL is not set")
		return nil, err
	}

	once.Do(func() {
		pool, err = connectToPgsql(ctx, connectionString)
	})

	return pool, err
}

currently it keeps calling os.getenv to retrieve connection string whenever getPool is called,

should it be implemented by also putting err in a global variable?