How to set a timer in solidity?

Question

I am launching a game that should close after exactly 3 days/72 hours of initializing & deploying the contract.

My current thoughts are:

1. declare a variable, timestamp.
2. in the constructor, set the variable timestamp to block.timestamp
3. add 3 days worth of time [in milliseconds i presume] to the timestamp variable
4. do a require(block.timestamp < timestamp) in the game logic [users call a write function, so I can do it in there], so users cannot write the function if block.timestamp is past timestamp + 3 days

Is this is a feasible solution? Is there a better solution? Is there a more gas efficient solution?

Thanks in advance

Answer 1

I just wrote this:

  // SPDX-License-Identifier: MIT

    pragma solidity 0.8.0;
    contract MyContract{
        uint start;
        uint end;
        modifier timeIsOver{
            require(block.timestamp<=end,"Time is up");
            _;
        }
         // Firstly, call this 
        function startTimer() public{
            start=block.timestamp;
        }
        // Secondly, call this 
        // timestamp of the current block in seconds since the epoch
        // period is in seconds
        function endTimer(uint period) public {
            end=period+start;
        }

        function timeLeft() public view returns(uint){
            return end-block.timestamp;
        }

        function callThisWhenTimeIsUp() external timeIsOver{
            // write the logic here
        }

    }

Or you could use oracle to set up timer. Oracle is external serice that you use in ethereum. an example: https://blog.chain.link/blockchain-voting-using-a-chainlink-alarm-clock-oracle/