Problem mysqli_fetch_assoc () | it's nothing to do with boolean;) [duplicate]

I'm new here, I have a problem in the code below: can someone give me a light?

Code.:

<tbody> 
   <?php
   while($linha = mysqli_fetch_assoc ($resultado))
   {
      echo '<tr>';
      echo '<td>'. $linha['ID'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '</tr>'; 
   }    
   mysqli_close ($conexao);     
   ?>
</tbody>

Error.:

  

Warning: mysqli_fetch_assoc () expects parameter 1 to be mysqli_result,   null given in   /home/u666149583/public_html/bootstrap/motorista/listar.php on line 70