getHash function
Implementation
String getHash(String keyS,String value){
// print("this is sthe va;ue");
// print(value);
// var key = utf8.encode(keyS);
var key=hex.decode(keyS);
var bytes = utf8.encode(value);
var hmacSha256 = Hmac(sha256, key); // HMAC-SHA256Txn-1234
var digest = hmacSha256.convert(bytes);
return digest.toString().toUpperCase();
}