How do you Change Direction of a Shot towards Mouse Position? (Top Down Shooter)

Hi

Making a top down space like shooter, got the player moving how I like it and I've set the mouse up so that the game can see it and everything. Got my shot set up and now I just want to fire it. I would like to be able to get this shot to fire towards the curser is possible.

I've managed to get the shot to instantiate at the shotSpawn location but i'm unsure on how to change its direction? In the code, mousePos stores where my curser is, I would have though I could just put that into a parameter of either the instantiate code or the mover code but apparently not the way I did it. Could anyone offer any suggestions please?

Cheer :)

PlayerController is the script attached to my Player Game Object.

 using UnityEngine;
 using System.Collections;
 
 ublic class PlayerController : MonoBehaviour 
 {
     //handling
     public float rotationSpeed = 450;
     public float speed = 20;
     public float fireRate;
     public Transform input;
 
     private float nextFire;
 
 
     //system
     private Quaternion targetRotation; //stores direction
     public PlayerBoundary boundary;
 
 
     //components
     private CharacterController controller;
     private Camera cam;
 
     public GameObject shot;
     public Transform shotSpawn;
 
 
     
     
     void Start()
     {
         controller = GetComponent<CharacterController> ();
         cam = Camera.main;
         
     }
     
 
     void Update()
     {
         if (Input.GetButton ("Shoot") && Time.time > nextFire) 
         {
             nextFire = Time.time + fireRate;
             Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
 
 
         
         
         }
     }
 
 
     void FixedUpdate()
     {
 
         ControlMouse ();
         //ControlWASD();
 
     
  
     }
 
 
 
     void ControlMouse()
     {
         //set up direction in input variabe
         Vector3 input = new Vector3(Input.GetAxisRaw("Horizontal"),0, Input.GetAxisRaw("Vertical")); 
 
 
         if (input != Vector3.zero) //fingers taken off controls, player doesnt reset to defaul position
         {
             targetRotation = Quaternion.LookRotation(input); //rotates player in the way of the direction
             transform.eulerAngles = Vector3.up * Mathf.MoveTowardsAngle(transform.eulerAngles.y, targetRotation.eulerAngles.y, rotationSpeed * Time.deltaTime);
             
         }
 
         //Controls Movement 
         Vector3 motion = input;
         motion *= (Mathf.Abs (input.x) == 1 && Mathf.Abs (input.z) == 1) ? .7f : 1; //moving diagonally doesnt travel at twice the speed
 
         controller.Move (motion * speed * Time.deltaTime);
 
 
         //Sets up mouse position
         Vector3 mousePos = Input.mousePosition;
         mousePos = cam.ScreenToWorldPoint (new Vector3 (mousePos.x, mousePos.y, cam.transform.position.y - transform.position.y));
 
 
     }

Mover has been set up on the Shot itself.

 using UnityEngine;
 using System.Collections;
 
 public class Mover : MonoBehaviour
 {
     public float speed;
     
     void Start ()
     {
         rigidbody.velocity = transform.forward * speed;
     }
 }