#include <Servo.h>
Servo myservo;
int pos = 00;   
         
void setup() {
 pinMode(8, INPUT_PULLUP);
 myservo.attach(9);
}
 
void loop(){ 
  if (digitalRead(8)==LOW){
 for(pos = 00; pos < 90; pos += 1)  
 {
  myservo.write(pos); 
  delay(20);              
 } 
  }
 if (digitalRead(8)==LOW){
 for(pos = 90; pos>=1; pos-=1)  
 {                              
  myservo.write(pos);                 
  delay(20);                        
 }
  }
}