#define BUTTON_PIN 26  // ESP32 pin GPIO22 connected to button's pin
#define RELAY_PIN  18  // ESP32 pin GPIO27 connected to relay's pin

// variables will change:
int relay_state = LOW;  // the current state of relay
int button_state;       // the current state of button
int last_button_state;  // the previous state of button

void setup() {
  Serial.begin(9600);                // initialize serial
  pinMode(BUTTON_PIN, INPUT_PULLUP); // set ESP32 pin to input pull-up mode
  pinMode(RELAY_PIN, OUTPUT);        // set ESP32 pin to output mode
  digitalWrite(RELAY_PIN, relay_state);
}

void loop() {
  last_button_state = button_state;      // save the last state
  button_state = digitalRead(BUTTON_PIN);   // read new state
  if (last_button_state == HIGH && button_state == LOW) {
    Serial.println("The button is pressed");

    // toggle state of relay
    relay_state = !relay_state;

    // control relay arccoding to the toggled state
    digitalWrite(RELAY_PIN, relay_state);
  }
  delay(50);
}