loop an animation if the button witch activates it is still pressed

I am starting a game and i have a animation manager code that activates an anim when i press a number or (in these case the left control). Well my problem is that when i press left controll the player crouch, and if i stop presing these button, the player gets up again, but when the anim of crouch idle ends the player gets up even if i continue pressing left controll. I have tried to put getkey instead of getkeydown but like these the anim dosn't play because is like all the time startig it.

this is my code:

 using UnityEngine;
 using System.Collections;
 
 public class player : MonoBehaviour {
 
     public Animator anim;
 
     CharacterController charactercollider;
 
     void Start ()
     {
         anim = GetComponent<Animator>();
 
         charactercollider = gameObject.GetComponent<CharacterController>();
     }
 
     void Update()
     {
         if (Input.GetKeyDown("1"))
         {
             anim.Play("standing_idle_02_looking", -1, 0f);
         }
         if (Input.GetKeyDown("2"))
         {
             anim.Play("standing_idle_03_examine", -1, 0f);
         }
         if (Input.GetKeyDown(KeyCode.LeftControl))
         {
             anim.Play("crouch_idle_01", -1, 0f);
         }           
         else
         {
             if ((Input.GetKeyUp(KeyCode.LeftControl)))
             {
                 anim.Play("standing_idle_01", -1, 0f);
             }
         }
         
         
     }
 }

i'm sorry for my eanglish, i'm not very pro that way.