Simple currency exchanges retrieval script. from USD to BRL,EUR using cli flags

currency.go

package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
)

var (
	url        string
	path       string
	currencies bool
	from       string
	to         string
	amount     float64
)

func checkFlags() {
	flag.BoolVar(&currencies, "currencies", false, "--currencies=true")
	flag.StringVar(&from, "from", "USD", "--from=USD")
	flag.StringVar(&to, "to", "BRL,EUR", "--to=BRL,EUR")
	flag.Float64Var(&amount, "amount", 0.0, "--amount=1.99")
	flag.Parse()
}

func makeRequest(path string) string {
	fmt.Println("Please wait... ")
	resp, err := http.Get(path)
	if err != nil {
		log.Fatal(err)
		os.Exit(1)
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Fatal(err)
		os.Exit(1)
	}

	return string(body)
}

func getCurrencies(url string) string {
	path = fmt.Sprintf("%v/currencies", url)
	return makeRequest(path)
}

func getLatestAmountFromTo(url string, amount float64, from string, to string) string {
	amountValue := ""
	if amount > 0 {
		amountValue = fmt.Sprintf("amount=%v&", amount)
	}
	path = fmt.Sprintf("%v/latest?%vfrom=%v&to=%v", url, amountValue, from, to)

	return makeRequest(path)
}

func main() {
	url = "https://api.frankfurter.app"
	checkFlags()

	if currencies {
		fmt.Println(getCurrencies(url))
		os.Exit(0)
	}

	fmt.Println(getLatestAmountFromTo(url, amount, from, to))
	os.Exit(0)
}