Referencing floating variables from another script? C#

So i am trying to get ID from the script "ContainerController", to ContainerTrigger". I know you have to do it with GetComponent, but it returns the error:

NullReferenceException: Object reference not set to an instance of an object ContainerTrigger.OnMouseDown () (at Assets/Prefabs/Containers/Scripts/ContainerTrigger.cs:9) UnityEngine.SendMouseEvents:DoSendMouseEvents(Int32)

The script is for if you click a spawned container, which are spawned with a for loop, you get the ID in the log. If i make a temp ID in the trigger script, it works fine. So yeah, im just not sure what im doing wrong with the GetComponent here XD (Yeah, fairly new to C# =p)

ContainerController:

 using UnityEngine;
 using System.Collections;
 
 public class ContainerController : MonoBehaviour {
 
     public GameObject[] containers1; 
     public GameObject[] containers2; //So you can (for example) Put dirty, open etc. Containers in that area
     private int Pos1y;
     private int Pos1x;
     private int Pos1z;
     private int Pos2y;
     private int Pos2x;
     private int Pos2z;
     private int ContRotx = -90;
     public float id;
 
     void Start()
     {
         //Spawning Containers at Position 1
         for (Pos1y = 2; Pos1y < 20; Pos1y += 4)
         {
             for (Pos1x = 0; Pos1x < 45; Pos1x += 12)
             {
                 for (Pos1z = 50; Pos1z < 60; Pos1z += 4)
                 {
                     GameObject container1 = containers1[Random.Range(0, containers1.Length)];
                     Instantiate(container1, new Vector3(Pos1x, Pos1y, Pos1z), Quaternion.Euler(ContRotx, 0,0));
                     id = id + 1;
                 }
             }
         }
 
         // Spawning at Another position, with a different set of containers.
         for (Pos2y = 2; Pos2y < 30; Pos2y += 4)
         {
             for (Pos2x = 0; Pos2x < 30; Pos2x += 12)
             {
                 for (Pos2z = 0; Pos2z < 30; Pos2z += 4)
                 {
                     GameObject container2 = containers2[Random.Range(0, containers2.Length)];
                     Instantiate(container2, new Vector3(Pos2x, Pos2y, Pos2z), Quaternion.Euler(ContRotx, 0, 0));
                     id = id + 1;
                 }
             }
         }
 
         // Trying for diff pos, fail or no? idk!
         for (Pos2y = 2; Pos2y < 30; Pos2y += 4)
         {
             for (Pos2x = 0; Pos2x < 30; Pos2x += 12)
             {
                 for (Pos2z = 100; Pos2z < 130; Pos2z += 4)
                 {
                     GameObject container2 = containers2[Random.Range(0, containers2.Length)];
                     Instantiate(container2, new Vector3(Pos2x, Pos2y, Pos2z), Quaternion.Euler(ContRotx, 0, 0));
                     id = id + 1;
                 }
             }
         }
     }
 }

Annd ContainerTriger:

 using UnityEngine;
 using System.Collections;
 
 public class ContainerTrigger : MonoBehaviour
 {
     void OnMouseDown() //When Container Clicked, it shows something in the debug log :D
     {
         ContainerController containerController = GetComponent<ContainerController>();
         Debug.Log(containerController.id);
     }
 }

Also it works fine if i spawn the ID's straight from the containercontroller, but thats not what i want :p Small edit: The ContainerController does have the tag "ContainerController".