int pin_led = 2;
int pin_btn = 17;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(pin_led, OUTPUT);
  pinMode(pin_btn, INPUT_PULLDOWN);
}

void loop() {
  if(digitalRead(pin_btn) == HIGH){
    digitalWrite(pin_led, HIGH);
  } else {
    digitalWrite(pin_led, LOW);
  }
}