Gate io error INVALID_SIGNATURE in app script

Question

I try to get data from Exchange Gate.io by app script. This is my code:

function data() {
var key = "***"
var sec = "***"
var timestamp = Math.floor(Date.now() / 1000)

var base = "https://api.gateio.ws";
var prefix = "/api/v4"
var pat = '/wallet/total_balance'

var sign = "timestamp=" + timestamp;

Logger.log(sign)


  var signature = Utilities.computeHmacSignature(Utilities.MacAlgorithm.HMAC_SHA_512, sign, sec);
  signature = signature.map(function(e) {
    var v = (e < 0 ? e + 256 : e).toString(16);
    return v.length == 1 ? "0" + v : v;
}).join("");
 

    var params = {
        'method': "get",
        'headers': {
                      'Accept': 'application/json', 
                      'Content-Type': 'application/json',
                       'KEY': key, 
                       'Timestamp': timestamp,
                       'SIGN': signature,
                       
                      },
        'muteHttpExceptions': true,
    };

   var data = UrlFetchApp.fetch(base + prefix + pat, headers=params);
   Logger.log(data)

}

I get the error:

{"label":"INVALID_SIGNATURE","message":"Signature mismatch"}

The Keys is valid problem in code.

to learn more check that: https://www.gate.io/docs/apiv4/en/#retrieve-user-s-total-balances