My code wont work for a projectile following a target

the vector3 wont update and I cant figure out how to make it work. we have a projectile that spins around the map but the target's position won't change this is the code: using System.Collections; using System.Collections.Generic; using UnityEngine;

public class CanonBallMoveTo : MonoBehaviour {

 public Transform target;
 public float speed;
 Vector3 targetVec = Input.mousePosition;
 // Use this for initialization
 void Start () {
     Vector3 targetVec = Input.mousePosition;
     speed = 10f;
     //target = GetComponent<Transform> ();

     targetVec = target.position;
 }

 // Update is called once per frame
 void Update () {

     Debug.Log (targetVec);
     StartCoroutine(moveTo(targetVec));
     //StartCoroutine(moveTo(new Vector3(-103.5713f, 4.707786f, 0)));
 }


 IEnumerator moveTo(Vector3 pos) {
     transform.position = Vector3.MoveTowards (transform.position, pos , speed * Time.deltaTime);
     yield return null;   
 }
     

}