#include <Servo.h>

Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards

int pos = 0;    // variable to store the servo position 0 to 180 degrees
int delta = 1;

void setup() {
  pinMode(10, INPUT_PULLUP);
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
  myservo.write(pos); 
  delay(200);
}

void loop() {
  if (digitalRead(10) == LOW) {
    delta = 0;
  }
  
  pos = pos + delta;
  if (pos >= 180) {
    delta = -1;
  } else if (pos <= 0) {
    delta = +1;
  }
  myservo.write(pos);              // tell servo to go to position in variable 'pos'
  delay(5);
}