title: Return value from callback in function
body: <p>Hello i would like to return a simple Boolean with there options:
  - true: user exists in database
  - false: user doesn't exists in database</p>
  
  <p>Here's my non-working code:</p>
  
  <pre><code>database.users.get("test-username", function (err, value) {
      if (err) {
          return err;
      } else {
          return value;
      }
  })
  </code></pre>
  
  <p>The return is always <code>undefined</code>
  I know that NodeJS is designed to work async, but async functions don't allow me to return something. I'm stuck, please help!</p>
  
  <p>Also, i use <code>LevelUP</code> as database system.
  (if my problem have no solution, is there an other database system in NodeJS that allow synchronous?)</p>
  
  <p>Thanks to the community!</p>