all the refactor

pkg/checkout/mutation_initialize_checkout.go

@@ -47,7 +47,7 @@ func HandleInitializeCheckout(g *CheckoutGrain, m *messages.InitializeCheckout)
 	}
 
 	g.CartTotalPrice = g.CartState.TotalPrice
-	g.AmountInCentsRemaining = g.CartTotalPrice.IncVat
+	g.AmountInCentsRemaining = g.CartTotalPrice.IncVat.Int64()
 
 	return nil
 }

pkg/checkout/mutation_payment_completed.go

@@ -36,7 +36,7 @@ func HandlePaymentCompleted(g *CheckoutGrain, m *messages.PaymentCompleted) erro
 
 	// Update checkout status
 	g.PaymentInProgress--
-	sum := g.CartState.TotalPrice.IncVat
+	sum := g.CartState.TotalPrice.IncVat.Int64()
 
 	for _, payment := range g.SettledPayments() {
 		sum -= payment.Amount