How to add shoot cooldown?

Unity Engine
1

I want to add a shoot cooldown to my single shot gun

heres the code

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using TMPro;

public class SingleShotGun : MonoBehaviour
{
    public TMP_Text hitText;

    public float damage = 10f;
    public float range = 100f;
    bool shot;
   
    public Camera fpsCam;
    public GameObject hitmarker;

    public float shotsFired;
    public float shotsHit;


    void Start()
    {
    shot = false;
    }

    // Update is called once per frame
    void Update()
    {
        if(Input.GetButtonDown("Fire1"))
    {
        SingleShotShoot();
    }

    if(shot)
    {
        StartCoroutine("hitmarkerShow");
    }

    hitText.text = shotsHit + "/" + shotsFired;
    }

    void SingleShotShoot()
    {
    shotsFired += 1;
    RaycastHit hit;
    if(Physics.Raycast(fpsCam.transform.position, fpsCam.transform.forward, out hit, range))
    {
        Debug.Log(hit.transform.name);
        shot = true;
        shotsHit += 1;
    }
    }

    IEnumerator hitmarkerShow()
    {
    hitmarker.SetActive(true);
    yield return new WaitForSeconds(0.05f);
    hitmarker.SetActive(false);
    shot = false;
    }
}

could someone show me how to do it

2

Cooldown timers, gun bullet intervals, shot spacing, rate of fire:

GunHeat (gunheat) spawning shooting rate of fire: