Singleton.cs

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

public abstract class Singleton<T> : MonoBehaviour where T : Component {

    private static T instance;

    public static T Instance {
        get {
            if (instance == null) {
                instance = FindObjectOfType<T>();
                if (instance == null) {
                    GameObject obj = new GameObject();
                    obj.name = typeof(T).Name;
                    instance = obj.AddComponent<T>();
                }
            }
            return instance;
        }
    }

    protected virtual void Awake() {
        if (instance == null) {
            instance = this as T;
			Init();
            DontDestroyOnLoad(gameObject);
        } else {
            Destroy(gameObject);
        }
    }

	public abstract void Init();

}