nodejs async main function

function async_main() {

    var args = process.argv.slice(2);
    
    let [file_name, ...file_paths] = args;

    fs.readFile(file_name, (err, data) => {
        if (err) throw err;
        let new_data = data.toString();
        for (let fp of file_paths) {
            console.log(new_data.replace("world", fp));
        }
    })
}