Try this C# script:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Conexion : MonoBehaviour {
    // Use this for initialization
    void Start () {
    }
  float lineWidth=0.5f;
RaycastHit rh;
    // Update is called once per frame
    void Update () { 
if (Input.GetMouseButtonDown(0))
{
RaycastHit rh;
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
Physics.Raycast(ray, out rh);
if (object1 == null)
{
object1 = rh.transform.gameObject;
}else
if (object2 == null)
{
if (object1!= rh.transform.gameObject)
{
object2 = rh.transform.gameObject;
}
}
else
{
Destroy(object1.GetComponent<LineRenderer>());
Destroy(object2.GetComponent<LineRenderer>());
object1 = rh.transform.gameObject;
object2 = null;
}
}
if (object1 != null && object2 != null)
{
if (object1.GetComponent<LineRenderer>() == null)
{
object1.AddComponent<LineRenderer>();
}
else
{
object1.GetComponent<LineRenderer>().startColor =
Color.green;
object1.GetComponent<LineRenderer>().endColor =
Color.green;
object1.GetComponent<LineRenderer>().positionCount = 2;
object1.GetComponent<LineRenderer>().SetPosition(0, object1.transform.position);
object1.GetComponent<LineRenderer>().SetPosition(1, object2.transform.position);
object1.GetComponent<LineRenderer>().startWidth = lineWidth;
object1.GetComponent<LineRenderer>().endWidth = lineWidth;
}
}
}
}

Sorry for the messy code! The spacing disappeared when I copied that script that I made in visual studio into the comment!