[HOW] Quit the game only after pressing Back button TWICE

I am making an android game. As a norm I think pressing the back button twice should close the application and thats what I aim to do in my game. However, I am not sure of how to code so that the if condition for the first time back button is pressed won’t be skipped and cause the game to quit straight away.
This is what I have now:

void Update()
    {

        if (Input.GetKey(KeyCode.Escape))
        {
            isPaused = true;
            pauseGame();

            if (Input.GetKey(KeyCode.Escape))
            {
                Application.Quit();
            }
        }
    }

Here is the code

    int click = 0;
    void Update()
    {
        if (Input.GetKeyDown(KeyCode.Escape))
        {
            click++;
            StartCoroutine(ClickTime());

              if (click > 1)
              {
                  print("Exit Game!");
              }
        }
    }
    IEnumerator ClickTime()
    {
        yield return new WaitForSeconds(0.5f);
        click = 0;
    }

You have basically 2 mistakes in your code.

Input.GetKey() returns true every time Update is called and the key is pressed… Just check the Unity Manual if you have trouble with Unity’s funtions. Since Update is called all the time in rapid succession, it’s very probable that the user will have the key pressed during multiple Update() calls even if he tries to press it very quickly. Use Input.GetKeyDown() instead because that happens only once when the button is pressed and doesn’t happen again until it’s released and pressed again.

The second issue is that even with GetKeyDown() both your if’s will happen at once because the condition in them is the same.

You already pause your game when the button is pressed. Just use that as the condition for the second press.

private void Update() {
		if (Input.GetKey(KeyCode.Escape)) {
			if (!isPaused) { // if game is not yet paused, ESC will pause it
				isPaused = true;
				pauseGame();
			} else { // if game is paused and ESC is pressed, it's the second press. QUIT
				Application.Quit();
			}
		}
	}