function setController(address _controller) public override onlyOwner {
    require(_controller != address(0), "ERROR_ZERO_ADDRESS");

    if (address(controller) != address(0)) {
        controller.migrate(address(_controller));
        controller = IController(_controller);
    } else {
        controller = IController(_controller);
    }

    emit ControllerSet(_controller);
}
function utilize() external override returns (uint256 _amount) {
    if (keeper != address(0)) {
        require(msg.sender == keeper, "ERROR_NOT_KEEPER");
    }
    _amount = available(); //balance
    if (_amount > 0) {
        IERC20(token).safeTransfer(address(controller), _amount);
        balance -= _amount;
        controller.earn(address(token), _amount);
    }
}
