Auto-Opening Trash Can

#include <Servo.h>
Servo cover;
const int trigPin=3;
const int echoPin=2;
long dist;
long dura;
void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  cover.attach(7);
  cover.write(0);
  Serial.begin(9600);
}
void loop(){
  ultra();
  opening();
}
void ultra() {

  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
 
  dura = pulseIn(echoPin, HIGH);
  dist = dura*0.034/2;
  Serial.println("distance="+String(dist));
}
void opening(){
  if(dist < 8){
    cover.write(110);
  }
  else{
    cover.write(0);
  }
}