code: func price(unit string, amount string) string {
  	if len(amount) == 0 {
  		return amount
  	}
  	if amount[0] == '-' {
  		amount = amount[1:]
  	} else {
  		amount = "-" + amount
  	}
  	for strings.Contains(amount, ".") && strings.HasSuffix(amount, "0") {
  		amount = amount[:len(amount)-1]
  	}
  	if strings.HasSuffix(amount, ".") {
  		amount = amount[:len(amount)-1]
  	}
  	unit = strings.ToUpper(unit)
  	if sym, ok := symbols[unit]; ok {
  		return sym + amount
  	} else {
  		if unit == "" {
  			return amount
  		}
  		return unit + " " + amount
  	}
  }
docs: // Price flips the sign of the amount and prints it with a currency symbol for
  // the given unit.