mecanim run animation script trouble

Hi i have this trouble:

     var Animator = Animator;
     
     function Update(){
     animations();
     }    
     
     function animations(){
     if (Input.GetKeyDown(KeyCode.LeftShift)) {
         
             if (Input.GetKeyDown("W"))
             {
             Animator.SetBool("run", true);
             }
             }
     }

this is my code, iam a novice in js so please dont be rude, the thing is i want to play the "run" animation when the Left Shift and the W key are pressed, the 2 at the same time like this logic:

w + shift = 1

only w = 0

only shift = 0

else = 0

or something like that... with my short knowledge of js i think that code is right, but doesnt work...

i also try this:

 if ((Input.GetKeyDown(KeyCode.LeftShift))&&(Input.GetKeyDown("w"))) { ...

but doesnt work too...

in the mecanim i have just boolean parameters to make it more easier... so when you play a certain button or key, the parameter change to true or false depends on the case and the animation can crossover...

anyone can help me :( ?