Double tap to dash (With Multiple keypress)

Hi i am trying to implement a keyboard double tap features to dash my character. I encounter a problem of detecting diagonal key press which involve 2 key press. Example (up and Left key) within a frame. so that will detect diagonal. Problem is i am having trouble trying to detect 2 keypresses within 1 frame. I tried implementing a buffer to detect the next keypress before double tap but it has a very low success rate.

 > if(Horizontal != 0)         
 >{
 >      bufferTime = Time.time;
 >         bufferOn = true;             
 >         bufferCount = 1; 
 >         lastTapTime = Time.time;
 >         keyInput |= (Horizontal < 0) ? keyDirection.Left : keyDirection.Right;
 >     }         
 >else if(Vertical !=0)         
 >{             
 >          bufferTime = Time.time;
 >         bufferOn = true;             
 >          bufferCount =2; 
 >         lastTapTime = Time.time;
 >         keyInput |= (Vertical < 0) ? keyDirection.Bottom : keyDirection.Top;
 >     }
 >     if (bufferOn == true)         
 > {             
 >      if(Vertical != 0 && bufferCount == 1)
 >      {
 >         keyInput |= (Vertical < 0) ? keyDirection.Bottom : keyDirection.Top;
 >         lastTapTime = Time.time;
 >         keyPressed = true;
 >         bufferCount = 0;
 >         }             
 >      else if (Horizontal != 0 && bufferCount == 2)             
 >      {
 >         keyInput |= (Horizontal < 0) ? keyDirection.Left : keyDirection.Right;
 >         lastTapTime = Time.time;
 >         keyPressed = true;
 >         bufferCount = 0;
 >          }             
 >   else             
 >   {
 >         bufferCount = 0;
 >         keyPressed = true;
 >         lastTapTime = Time.time;
 >   }         
 >}
 

Btw i don't need the user to keep holding on the buttons because i just want user to double tap and let the code (or player object) do the rest of the dash. So it's only tap, not hold.