How to make goalKeeper move within post but not move towards to the player?

Hello so basically I make a 2d top-down soccer game but I have to trouble with GK AI, I want to GK is followed the ball but not move toward on it

let say (Enemy = GK)

so when the player moves to the left or right the enemy will follow to the right or left not The Yaxis but in X-axis with guarding the post or Y=0

my default enemy movement is like this :

if (gameObject.CompareTag("GK"))         {              anim.SetBool("GKRun", false);             gkballInRange = Physics2D.OverlapCircle(transform.position, gkballRange, playerMask);             float distancePlayer = Vector2.Distance(target.position, transform.position);              if (gkballInRange)             {                 if (distancePlayer <= gkballRange)                 {                     //Animation                     anim.SetBool("GKRun", true);                     transform.Translate(0, -speed * Time.deltaTime, 0);                 }             }          } 

in that scrip, when the ball is on the range the GK is moving to the ball just that. maybe anyone can explain to me how to do it?