title: vert.x async jdbc doesn't close connections
body: <p>I'm implementing a RESTful API with Vert.x. I used its async jdbc client with MySQL and c3p0 as connection pool.</p>
  
  <p>My problem is that although the closeConnection handler is successful, the actual database connection is not closed and reused. The pool gets full in seconds, resulting in: <em>BasicResourcePool:204 - acquire test -- pool is already maxed out. [managed: 20; max: 20]</em></p>
  
  <pre><code>client.getConnection(connectionAsyncResult -&gt; {
  SQLConnection connection = connectionAsyncResult.result();
  connection.queryWithParams("SELECT * FROM AIRPORTS WHERE ID = ?", new JsonArray().add(id), select -&gt; {
      ResultSet resultSet = select.result();
      Airport $airport = resultSet.getRows()
              .stream()
              .map(Airport::new)
              .findFirst()
              .get();
  
      asyncResultHandler.handle(Future.succeededFuture($airport));
      connection.close(closeHandler -&gt; {
          if (closeHandler.succeeded()) {
              LOG.debug("Database Connection closed");
          }
          else if (closeHandler.failed()) {
              LOG.error("Database Connection failed to close!");
          }
      });
  });
  </code></pre>
  
  <p>});</p>
  
  <p>Any idea what I'm missing?</p>
  
  <p>All the best!</p>