Find closest waypoint.

I use the following script to find the closest waypoint for my NPCs to go to. However, the debug logs a list of all the checkpoints and the NPCs do not move to the closest one but to the last one in the list.

   GameObject[] checkpoint = GameObject.FindGameObjectsWithTag("checkpoint");
                 {
                     foreach (GameObject go in checkpoint)
                     {
                         ObjectiveControl comp = go.GetComponent<ObjectiveControl>();
                        if (comp != null && comp.waypoint == true*/)
                         {
                             path.Add(comp.transform);
                             currentCheckpoint = FindClosestCheckpoint();
                             Debug.Log(currentCheckpoint);
                         }
                     }
                 }
 
    int FindClosestCheckpoint()
     {
             if (path.Count == 0) return -1;
             int closest = 0;
             float lastDist = Vector3.Distance(this.transform.position, path[0].transform.position);
             for (int i = 1; i < path.Count; i++)
             {
                 float thisDist = Vector3.Distance(this.transform.position, path[i].position);
                 if (lastDist > thisDist && i != currentCheckpoint)
                 {
                     closest = i;             
                 }
             }
             return closest;
         }