Added null cheque

vchasno.go

@@ -274,3 +274,23 @@ func (c *Client) QuickSellNamed(ctx context.Context, name string, price float64)
 		Price: price,
 	})
 }
+
+func (c *Client) ZeroReceipt(ctx context.Context) (*api.SellResponse, error) {
+	return c.api.Sell(ctx, api.SellParams{
+		Cashier:   c.cashier,
+		Source:    c.source,
+		Rows:      []api.ReceiptRow{},
+		Pays:      []api.ReceiptPay{},
+		CommentUP: "Нульовий чек",
+	})
+}
+
+func (c *Client) ZeroReceiptWithTimeout(timeout time.Duration) (*api.SellResponse, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+	return c.ZeroReceipt(ctx)
+}
+
+func (c *Client) ZeroReceiptDefault() (*api.SellResponse, error) {
+	return c.ZeroReceiptWithTimeout(c.defaults.DefaultTimeout)
+}