u3d-space-shooter/Assets/Scripts/SpawnManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SpawnManager : MonoBehaviour
{
    [SerializeField]
    private GameObject enemyPrefab;
    [SerializeField]
    private GameObject enemyContainer;

    private bool stopSpawning = false;

    void Start()
    {
        StartCoroutine(SpawnRoutine());
    }

    IEnumerator SpawnRoutine()
    {
        while (!stopSpawning)
        {
            Vector3 posToSpawn = new Vector3(Random.Range(-8f, 8f), 7, 0);
            GameObject newEnemy = Instantiate(enemyPrefab, posToSpawn, Quaternion.identity);
            newEnemy.transform.SetParent(enemyContainer.transform);
            yield return new WaitForSeconds(5.0f);
        }
    }

    public void OnPlayerDeath()
    {
        stopSpawning = true;
    }
}