private void LoadSuppliers()
        {
            string           querry     = "SELECT * FROM supplier";
            SQLiteConnection connection = new SQLiteConnection(connectionString);

            using (SQLiteCommand command = new SQLiteCommand(querry, connection))
            {
                connection.Open();
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        long     id             = (long)reader["id"];
                        string   s_name         = (string)reader["s_name"];
                        int      inregistration = Convert.ToInt32(reader["s_inregistration"]);
                        string   bank           = (string)reader["s_bank"];
                        string   headquaters    = (string)reader["headquaters"];
                        string   phone          = (string)reader["s_phone"];
                        string   employee       = (string)reader["employee"];
                        Supplier supplier       = new Supplier(id, s_name, inregistration, bank, headquaters, employee, phone);

                        string goodsQuerry = $"Select * from good where supplier_id={id}";
                        using (SQLiteCommand goodCommand = new SQLiteCommand(goodsQuerry, connection))
                        {
                            using (var goodReader = goodCommand.ExecuteReader())
                            {
                                while (goodReader.Read())
                                {
                                    long         g_id        = (long)goodReader["g_id"];
                                    string       g_name      = (string)goodReader["g_name"];
                                    double       price       = Convert.ToDouble(goodReader["g_price"]);
                                    string       description = (string)goodReader["g_description"];
                                    bool         taxable     = bool.Parse(goodReader["taxable"].ToString());
                                    GoodCategory category    = (GoodCategory)Convert.ToInt32(goodReader["category"]);
                                    Good         good        = new Good(g_id, g_name, price, category, description, taxable);
                                    supplier.AddGood(good);
                                }
                            }
                        }

                        suppliers.Add(supplier);
                    }
                }
            }
        }