Keyless Entry with Elegoo

#include <SPI.h>
#include <MFRC522.h>
#include <Servo.h>

#define RST_PIN 5           
#define SS_PIN 53          
#define SERVO_PIN 2

MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance.

int card_uid[] = {0xFF,0xFF,0xFF, 0xFF}; //Change to match NFC card

MFRC522::MIFARE_Key key;

Servo lock;

void setup(){
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();
  for (byte i = 0; i < 6; i++) {
        key.keyByte[i] = 0xFF;
  }
  Serial.print(F("Using key (for A and B):"));
  dump_byte_array(key.keyByte, MFRC522::MF_KEY_SIZE);
  lock.attach(SERVO_PIN);
  lock.write(135);
  delay(400);
  lock.detach();
}

void loop(){
  if ( ! mfrc522.PICC_IsNewCardPresent()){
        return;}
  if ( ! mfrc522.PICC_ReadCardSerial()){
        return;}
  Serial.print(F("Card UID:"));
  dump_byte_array(mfrc522.uid.uidByte, mfrc522.uid.size);
  Serial.println("\n");
  Serial.println(check_uid(mfrc522.uid.uidByte, mfrc522.uid.size));
  Serial.println();
  Serial.print(F("PICC type: "));
    MFRC522::PICC_Type piccType = mfrc522.PICC_GetType(mfrc522.uid.sak);
    Serial.println(mfrc522.PICC_GetTypeName(piccType));
 delay(3000);
    
}


void dump_byte_array(byte *buffer, byte bufferSize) {
    for (byte i = 0; i < bufferSize; i++) {
        Serial.print(buffer[i] < 0x10 ? " 0" : " ");
        Serial.print(buffer[i], HEX);
    }
}

bool check_uid(byte *buffer, byte bufferSize){
  int correct = 0;
  for(byte i=0;i<bufferSize;i++){
    Serial.print(buffer[i]);
    Serial.print(" | ");
    Serial.println(card_uid[i]);
    if(buffer[i] == card_uid[i]){
      correct += 1;
    }
  }
  if(correct==4){
    Serial.println("Access granted");
    lock.attach(SERVO_PIN);
  lock.write(180);
  delay(10000);
  lock.write(135);
  delay(1000);
  lock.detach();
    return true;
  }
}