Mecanim animation keeps running infinite

I made a character controller with mecanim and I have an idlestate for idling, a locostate for walking and a runningstate for running. The transition from walking to running is a boolean called "Sprint". I want the character to run WHILE i press leftshift button on my keyboard, but now the character just keeps running when I pressed shift once. Thank you! This is my script:

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent(typeof (Animator))]
 [RequireComponent(typeof (CapsuleCollider))]
 [RequireComponent(typeof (Rigidbody))]
 
 public class ControlScript : MonoBehaviour
 {
     [System.NonSerialized]                    
     public float lookWeight;                                                    // the amount to transition when using head look
     
     public float animSpeed = 1.5f;                                                // a public setting for overall animator animation speed
     public float lookSmoother = 3f;                                                // a smoothing setting for camera motion
     
     private Animator anim;                                                        // a reference to the animator on the character
     private AnimatorStateInfo currentBaseState;                                    // a reference to the current state of the animator, used for base layer
     private AnimatorStateInfo layer2CurrentState;                                // a reference to the current state of the animator, used for layer 2
     private CapsuleCollider Col;                                                // a reference to the capsule collider of the character
 
     static int idleState = Animator.StringToHash("Base Layer.Idle");    
     static int locoState = Animator.StringToHash("Base Layer.Locomotion");        // these integers are references to our animator's states
     static int jumpState = Animator.StringToHash("Base Layer.Jump");            // and are used to check state for various actions to occur
     static int rollState = Animator.StringToHash("Base Layer.Roll");
     
     void Start()
     {
         // initialising reference variables
         anim = GetComponent<Animator>();                      
         Col = GetComponent<CapsuleCollider>();                
         if(anim.layerCount ==2)
             anim.SetLayerWeight(1, 1);
 
         rigidbody.mass = 60f;
         rigidbody.freezeRotation = true;
 
         Col.center = new Vector3(0, 1, 0);
         Col.radius = 0.3f;
         Col.height = 2f;
         gameObject.tag = "Player";
     }
     
     
     void Update()
     {
         float h = Input.GetAxis("Horizontal");                // setup h variable as our horizontal input axis
         float v = Input.GetAxis("Vertical");                // setup v variables as our vertical input axis
         anim.SetFloat("Speed", v);                            // set our animator's float parameter 'Speed' equal to the vertical input axis                
         anim.SetFloat("Direction", h);                         // set our animator's float parameter 'Direction' equal to the horizontal input axis        
         anim.speed = animSpeed;                                // set the speed of our animator to the public variable 'animSpeed'
         anim.SetLookAtWeight(lookWeight);                    // set the Look At Weight - amount to use look at IK vs using the head's animation
         currentBaseState = anim.GetCurrentAnimatorStateInfo(0);    // set our currentState variable to the current state of the Base Layer (0) of animation
         
         if(anim.layerCount == 2)        
             layer2CurrentState = anim.GetCurrentAnimatorStateInfo(1);    // set our layer2CurrentState variable to the current state of the second Layer (1) of animation
         
         
         //JUMPING
         //Idle to Jump
         if (currentBaseState.nameHash == idleState)
         {
             if(Input.GetButtonDown("Jump"))
             {
                 anim.SetBool("Jump", true);
             }
         }
         
         //Loco to Jump
         if (currentBaseState.nameHash == locoState)
         {
             if(Input.GetButtonDown("Jump"))
             {
                 anim.SetBool("Jump", true);
             }
         }
         
         //ROLLING
         //Idle to Roll
         if (currentBaseState.nameHash == idleState)
         {
             if(Input.GetKeyDown(KeyCode.LeftControl))
             {
                 anim.SetBool("Roll", true);
             }
         }
         
         //Loco to Roll
         if (currentBaseState.nameHash == locoState)
         {
             if(Input.GetKeyDown(KeyCode.LeftControl))
             {
                 anim.SetBool("Roll", true);
             }
         }
 
         //AVOID REPEATING
         //jumping
         if (currentBaseState.nameHash == jumpState)
         {
             anim.SetBool("Jump", false);
         }
 
         //rolling
         if(currentBaseState.nameHash == rollState)
         {
             anim.SetBool("Roll", false);
         }
 
         if (currentBaseState.nameHash == locoState)
         {
             if(Input.GetKey(KeyCode.LeftShift))
             {
                 anim.SetBool("Sprint", true);
             }
 
             else
             {
                 anim.SetBool("Sprint", false);
             }
         }
 
         if(currentBaseState.nameHash == idleState)
         {
             if(Input.GetKey(KeyCode.LeftShift))
             {
                 anim.SetBool ("Sprint", true);
             }
 
             else
             {
                 anim.SetBool("Sprint", false);
             }
         }
     }
 }