#include <Servo.h>

//Button
#define BUTTON_IN 5
#define SERVO_PIN 6

//Servo
Servo myservo; 

//Variables
int pos = 0;   
int servodelay = 500;
int add = 45;

void setup() {
  Serial.begin(9600);

  // Servo
  myservo.attach(SERVO_PIN);
  myservo.write(pos);

  //Button
  pinMode(BUTTON_IN, INPUT);
}

void loop() {

  int buttonState = digitalRead(BUTTON_IN);

  if (buttonState > 0) {

    if(pos >= 180) {
      add = add * -1;
    }

    pos = pos + add;    
    myservo.write(pos);  
    delay(servodelay);  

    if(pos <= 0) {
      add = add * -1;
    }
  }

}