功能設計：
添加一個lockTokens函數來允許持有者設定鎖定期，修改transfer函數來檢查是否達到解鎖時間，若未達到則拒絕轉移。

pragma solidity ^0.8.0;

contract MyToken {
    string public name = "My Token";
    string public symbol = "MTK";
    uint8 public decimals = 18;
    uint256 public totalSupply;
    address public owner;
    
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;
    mapping(address => uint256) public lockTime;  // 新增鎖定時間
    
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    constructor(uint256 _initialSupply) {
        totalSupply = _initialSupply * 10 ** uint256(decimals);
        balanceOf[msg.sender] = totalSupply;  // 初始化代幣
        owner = msg.sender;  // 設定合約擁有者
    }
    function transfer(address _to, uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value, "餘額不足");
        require(block.timestamp > lockTime[msg.sender], "代幣被鎖定中");
        
        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;
        
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    // 設置鎖定時間
    function lockTokens(uint256 _time) public {
        lockTime[msg.sender] = _time;
    }
}

測試與驗證：

• 部署合約後，使用lockTokens設定一個未來的時間。
• 測試轉移功能，確保在鎖定期間無法轉移代幣。
• 等待到鎖定期結束後，確認代幣可以正常轉移。