How to draw the trajectory (on which it moved) of the movement of an object in Unity 2D?

Question

Unity

I have a red circle, which should leave lines after itself, that is, the trajectory along which it moved. I wrote a small script and attached it to it, but something is not working.
My code:

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

public class Траектория : MonoBehaviour
{
    public Material mat;
    Vector2 start, end;

    void OnRenderObject()
    {
        end = transform.position;
        GL.PushMatrix();
        mat.SetPass(0);
        GL.LoadOrtho();

        GL.Begin(GL.LINES);
        GL.Color(Color.red);
        GL.Vertex(start);
        GL.Vertex(end);
        GL.End();

        GL.PopMatrix();

        start = end;       
    }

    void Start()
    {
        start = transform.position;
    }
}

What is available now:

What is approximately needed:

Answer 1

Trail Renderer

Answer 2

Already done, or help?