function adminCheck(inp) {
    fs.readFile('./files/admins', 'utf8', (err, data) => {
        if (err) {
            console.log(err);
        }
        if(data.includes(inp)){
            console.log('Admin')
            return true;
        }else{
            console.log('Non-admin')
            return false;
        }
    })
};

I want to check if a user is in the admin file. The console messages in the function are signaling correctly when I add/remove a username. But the function is not returning T/F when I call with:

console.log(adminCheck(request.session.username))

It just console logs "undefined" so I can't do anything with it, I cannot figure out why. Any thoughts?