Solidity smart contract for Election on Blockchain

Election.sol

pragma solidity >= 0.5.0 < 0.6.0;

// @author Andrej
// @title Election

contract Election {
    address payable public contractOwner;
    
     struct Candidate {
        string name;
        uint256 voteCount;
        bool exists; // default je false
    }
    
    mapping (string => Candidate) candidates;
    mapping (address => bool) public voters;
    
    event votedEvent (address _voter, string _candidate);
    
    modifier isOwner {
        require(msg.sender == contractOwner);
        _;
    }
    
    constructor() public {
        contractOwner = msg.sender;
    }
    
    function kill() isOwner public {
        selfdestruct(contractOwner);
    }
    
    modifier voteOnce {
        require(!voters[msg.sender], "You have already voted");
        _;
    }
    
    function addCandidate (string memory _name) public {
        candidates[_name].name = _name;
        candidates[_name].voteCount = 0;
        candidates[_name].exists = true;
    }
    
    function vote(string memory _name) public payable voteOnce {
        require(candidates[_name].exists, "Candidate does not exist");
        candidates[_name].voteCount++;
        voters[msg.sender] = true;
        emit votedEvent(msg.sender, _name);
    }
    
    function getVoteCount(string memory _name) public view returns(uint256) {
        return candidates[_name].voteCount;
    }

}