title: How to use Rails connection which is manually checkout
body: <p>I have code which where I manually checkout a connection like</p>
  
  <p><code>connection = User.connection_pool.checkout</code></p>
  
  <p>Now, I wish to use this connection to query any record in DB </p>
  
  <p>is there a way to achieve this. </p>
  
  <p>I'm not sure what I'm suppose to do with the connection, I just obtained other then checking it back in</p>
  
  <p>So ideally I want the code do this.</p>
  
  <pre><code>  connection = User.connection_pool.checkout
    ... ## query
  
    User.connection_pool.checkin(connection)
  </code></pre>
  
  <p><strong>Note</strong>: Please don't answer me to use <code>with_connection</code>, the point of this question is to manage checkout/checkin manually.</p>
  
  <p>Any clue ??</p>