tick method
      
void
tick()
      
     
    
Progress the bar by one tick towards its maxValue.
Implementation
void tick() {
  if (!_shouldDrawProgress) {
    return;
  }
  _tickCount++;
  final fractionComplete =
      math.max(0, _tickCount * _innerWidth ~/ maxValue - 1);
  final remaining = _innerWidth - fractionComplete - 1;
  final spinner =
      showSpinner ? tickCharacters[_tickCount % tickCharacters.length] : ' ';
  _printProgressBar(
      '[${tickCharacters[0] * fractionComplete}$spinner${' ' * remaining}]');
}