HDRP Skybox control

Unity Engine
1

Recently I added HDRP inside my project. After I figured out how to implement the skybox I wanted to make it rotate and change between night and day skybox. So I tried to add a script on the skybox object but I was not able to add a reference on the Volume(script) component. Any suggestions on how to control my HDRI sky?

4397080--399937--skybox inspector.png
4397080--399937--skybox inspector.png501×632 41 KB

2 
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.HighDefinition;

public class volume_control : MonoBehaviour
{

    [SerializeField] Volume volume;
    HDRISky sky;
    public Cubemap sky_1, sky_2;

    private void Start()
    {
        volume.profile.TryGet(out sky);
    }

    private void FixedUpdate()
    {
        /// ROTATE HDRI SKYBOX
        sky.rotation.value += 0.02f;
    }

    private void Update()
    {
        change_skybox();
    }

    public void change_skybox()
    {
        if (Input.GetKeyDown("1"))
        {
            /// CHANGE HDRI SKYBOX
            sky.hdriSky.value = sky_1;
        }
        else if (Input.GetKeyDown("2"))
        {
            sky.hdriSky.value = sky_2;
        }
    }
}