#include <Servo.h>
const byte ledPin = 13;
const byte interruptPin = 2;
const byte servoPin = 3;
volatile bool everythingWorkingFine = true;
Servo myservo;
void setup() {
  Serial.begin(115200);
  pinMode(ledPin, OUTPUT);
  pinMode(interruptPin, INPUT_PULLUP);
  myservo.attach(servoPin);
  attachInterrupt(digitalPinToInterrupt(interruptPin), somethingBroke, CHANGE);
}

void loop() {
  digitalWrite(ledPin, LOW);
  myservo.write(180);
  delay(500);
  myservo.write(90);
  delay(500);

  if(digitalRead(4)==HIGH)
  somethingBroke();
}

void somethingBroke() {
  while(true)
  {
  digitalWrite(ledPin, HIGH);
  }
}