#include <Servo.h>

Servo myServo;

void setup() {
  myServo.attach(8);
}

void loop() {
  for (byte angle = 0; angle < 180; angle++) {
    myServo.write(angle);
    delay(200);
  }
  for (byte angle = 180; angle > 0; angle--) {
    myServo.write(angle);
    delay(200);
  }
}