How do I sense when the player collides with a door in a GameController script?

Question

I want to be able to sense when the player collides with a door from my GameController script. The player is a public GameObject and doors are tagged as such. Here is psuedo code for what I'm looking for:

public class GameController : MonoBehaviour
{
   public GameObject player;

   void Update()
   {
      if(player collides with game object tagged "Door")
         do something
   }
}

Answer 1

Thank you @schneebuzz for helping me to fix this issue. With his advice I was able to find a function to manually check for collision with a rigidbody.

public class GameController : MonoBehaviour
{
    public GameObject player;
    public float collisionCheckDistance;

    private Rigidbody rigidbody;

    void Start()
    {
        rigidbody = player.GetComponent<Rigidbody>();
    }

    void Update()
    {
        RaycastHit raycastHit;

        if (rigidbody.SweepTest(rigidbody.transform.TransformDirection(Vector3.forward), out raycastHit, collisionCheckDistance))
        {
            if (raycastHit.transform.tag == "Door")
            {
                DoorController doorController = raycastHit.transform.gameObject.GetComponentInParent<DoorController>();
                doorController.openDoor();
                doorController.closeDoor();
            }
        }
    }
}

Answer 2

You need a collider (e.g. BoxCollider, CapsuleCollider etc.) on both the player and door and a script component on your Player:

public class MyPlayer : MonoBehaviour
{

   void OnCollisionEnter(Collision collision)
   {
        if(collision.gameObject.CompareTag("Door")
        {
            Debug.Log("Player Hit door, do something!");
        }
   }
}

As noted by @DMGregory: One of the two colliding components need an attached Rigidbody or CharacterController, in your case this is most likely the player.