Brazil's PIX CID Calculation in Golang

cid.go

package main

import (
	"fmt"
	"strings"

	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
)

func hmacSha256(key []byte, data []byte) []byte {
	r := hmac.New(sha256.New, key)
	r.Write([]byte(data))

	return r.Sum(nil)
}

func lowercaseHexadecimal(data []byte) string {
	return strings.ToLower(hex.EncodeToString(data))
}

func main() {

	var (
		keyType          string = "EMAIL"
		key              string = "[email protected]"
		ownerTaxIdNumber string = "01234567890"
		ownerName        string = "John Doe"
		ownerTradeName   string = ""
		participant      string = "00000001"
		branch           string = "0001"
		accountNumber    string = "1"
		accountType      string = "TRAN"
	)

	requestId := "c1e63c6a-7c9f-4be0-8413-4729ffe3e5ea"
	requestIdBytes, _ := hex.DecodeString(strings.ReplaceAll(requestId, "-", ""))

	entryAttributes := fmt.Sprintf("%s&%s&%s&%s&%s&%s&%s&%s&%s", keyType, key, ownerTaxIdNumber, ownerName, ownerTradeName, participant, branch, accountNumber, accountType)

	cidBytes := hmacSha256(requestIdBytes, []byte(entryAttributes))
	cid := lowercaseHexadecimal(cidBytes)

	fmt.Println("Request ID:", requestId)
	fmt.Println("Entry Attributes:", entryAttributes)
	fmt.Println("CID:", cid)
}