Continuous rotation on key press?

using UnityEngine;
using System.Collections;

public class Rotation : MonoBehaviour
{

// Use this for initialization
void Start()
{

}

// Update is called once per frame
public float turnSpeed = 50f;
void Update()
{
    if (Input.GetKey(KeyCode.A))
        transform.Rotate(Vector3.up * turnSpeed * Time.deltaTime);

    if (Input.GetKey(KeyCode.D))
        transform.Rotate(Vector3.up * -turnSpeed * Time.deltaTime);
}

}

this is my code i need help on how to make an infinite rotation but it will change its rotation when a specific key is pressed going left or going right

What do you mean with infinite? Keep rotating even if a key is not pressed? Then, try this…

public float turnSpeed = 50.0f;
void Update()
{
     transform.Rotate(Vector3.up * turnSpeed * Time.deltaTime);

     if (Input.GetKey(KeyCode.A))
          turnSpeed = 50.0f
     if (Input.GetKey(KeyCode.D))
          turnSpeed = -50.0f
}

oh thanks it works now sorry i am new to unity