How can i get my enemy spawner follow the player?

I'm trying to make my enemy spawner follow the player. At the moment its set to 40 on z but when the player moves past that they keep spawning in that 1 place.

here is the code so far:

 public class GameController : MonoBehaviour  {

 public GameObject hazard;
 public Vector3 spawnValues;
 public int hazardCount;
 public float spawnWait;
 public float startWait;
 public float waveWait;

 public GameObject player; //New follow code 
 private Vector3 OffSet; //New follow code

 private void Start()
 {
    StartCoroutine(SpawnWaves());
 }

 IEnumerator SpawnWaves() {
     yield return new WaitForSeconds (startWait);
     while (true) //infinate loop
     {
         for (int i = 0; i < hazardCount; i++)
         {
             LateUpdate();

             /* original spawn in 1 place code
             Vector3 spawnPosition = new Vector3(Random.Range(-spawnValues.x, spawnValues.x), spawnValues.y, spawnValues.z);
             Quaternion spawnRotation = new Quaternion();
             Instantiate(hazard, spawnPosition, spawnRotation);
             yield return new WaitForSeconds(spawnWait);
             */ original code

         }
         yield return new WaitForSeconds(waveWait);
     }
 }

 // New follow code
 void LateUpdate()
 {
     transform.position = player.transform.position + OffSet;   // New follow code
     Quaternion spawnRotation = new Quaternion();
     Instantiate(hazard, player.transform.position, spawnRotation);
     yield return new WaitForSeconds(spawnWait);
 }
 }

I get an error message saying "The body of 'GameController.LateUpdate()' cannot be an iterator block because 'void' is not an iterator interface type"

Does anyone have suggestion?