node.js

var program = require('commander');

process.stdin.resume()

program
    .version('0.1.1')
    .option('-i, --input [name]', 'User input')
    .parse(process.argv)

function dateHelloError(value) {
    return new Promice(function(resolve, reject) {
        switch (program.input) {
            case 'date':
                console.log(new Date());
                process.exit(2);
                break;
            case 'hello':
                setTimeout(function() {
                    console.log("hello world");
                    process.exit(2);
                }, 1000);
                break;
            default:
                console.log("Oh, g*vno! An error occured! Only 'date' or 'hello' appropriate.");
                process.exit(2);
                break;
        };
    })
}
dateHelloError(program.input);