package main

import (
	"fmt"
	"github.com/shopspring/decimal"
)

func main() {
	price, err := decimal.NewFromString("136.02")
	if err != nil {
		panic(err)
	}
	quantity := decimal.NewFromFloat(3)
	subtotal := price.Mul(quantity)
	fmt.Println("Subtotal:", subtotal)                      // Subtotal: 408.06
}