#include <Servo.h>

Servo myservo;  // create servo object
int button_pin = 2;
int button_value;
void setup() 
{
  myservo.attach(11);  
  pinMode(button_pin, INPUT_PULLUP);
}
void loop() 
{
  button_value = digitalRead(button_pin);

  if (button_value == 1) {
    myservo.write(90);
  } else if (button_value == 0) {
    myservo.write(0);
  }
  delay(100);
}