Do something when holding finger on screen mobile

I can't figure out how to create a script that when I press the screen and hold, something happens, and when I release my finger, that something stops happening. What I want to do is that when I press and hold, a 2d object with rigidbody2D goes up and when I am not pressing, the object goes down.

Here is a quick video of what I'm trying to achieve:

https://www.youtube.com/watch?v=IyRDnIfNQIo

So far I've found this script that tells the game when the screen is pressed (I think):

 using UnityEngine;
 using System.Collections;
 
 public class ChangeGravity : MonoBehaviour {
 
     private float holdTime = 0.8f; //or whatever
     private float acumTime = 0;
 
     void Update()
     {
         if (Input.touchCount > 0)
         {
             acumTime += Input.GetTouch(0).deltaTime;
 
             if (acumTime >= holdTime)
             {
                 gameObject.GetComponent<Rigidbody2D>().gravityScale = -1;
             }
 
             if (Input.GetTouch(0).phase == TouchPhase.Ended)
         {
                 acumTime = 0;
             }
         }
     }
 }
 

I thought of changing the gravity scale to -1 in the rigidbody2D every time the screen is pressed and then when I release the gravity scale changes back to 1 but I can't get it to work. The script is attached to a 2d gameObject with a rigidbody2D.

Thanks for the Help :)