Dictionary<KeyCode, System.Action> keyCodeDic = new Dictionary<KeyCode, System.Action>();

void Start()
{
    //Register Keycodes to match each function to call
    const int alphaStart = 48;
    const int alphaEnd = 57;

    int paramValue = 0;
    for (int i = alphaStart; i <= alphaEnd; i++)
    {
        KeyCode tempKeyCode = (KeyCode)i;

        //Use temp variable to prevent it from being capture
        int temParam = paramValue;
        keyCodeDic.Add(tempKeyCode, () => MethodCall(temParam));
        paramValue++;
    }
}

void MethodCall(int keyNum)
{
    Debug.Log("Pressed: " + keyNum);
}


void Update()
{
    //Loop through the Dictionary and check if the Registered Keycode is pressed
    foreach (KeyValuePair<KeyCode, System.Action> entry in keyCodeDic)
    {
        //Check if the keycode is pressed
        if (Input.GetKeyDown(entry.Key))
        {
            //Check if the key pressed exist in the dictionary key
            if (keyCodeDic.ContainsKey(entry.Key))
            {
                //Debug.Log("Pressed " + entry.Key);

                //Call the function stored in the Dictionary's value
                keyCodeDic[entry.Key].Invoke();
            }
        }
    }
}