#include <ESP32Servo.h>    // change this from Servo.h
#define SERVO_PIN 21 

Servo myservo;             // create servo object to control a servo

int pos = 0;               // variable to store the servo position
void setup() {
myservo.attach(SERVO_PIN); // change this to use the #define
}
void loop() {
  for (pos = 0; pos <= 180; pos += 1) {
    // goes from 0 degrees to 180 degrees
    // in steps of 1 degree
    myservo.write(pos);    // tell servo to go to position in variable pos
    delay(15);             // waits 15 ms for the servo to reach the position
  }

  for (pos = 180; pos >= 0; pos -= 1) {
    // goes from 180 degrees to 0 degrees
    // in steps of -1 degree
    myservo.write(pos);    // tell servo to go to position in variable pos
    delay(15);             // waits 15 ms for the servo to reach the position
  }
}