How to send attachment using mailgun?

Question

I am trying to send attachment using curl through mailgun but its sending email with out attachment.(I am receiving email with only html part but no attachments.) Here is my code

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
    curl_setopt($ch, CURLOPT_USERPWD, 'api:'.$api_key);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
    curl_setopt($ch, CURLOPT_URL, 'https://api.mailgun.net/v3/'.$domain.'/messages');
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $postFields);
    $result = curl_exec($ch);
    curl_close($ch);
    return $result;

$postFields is array with following value.

Array
(
    [from] => ***
    [to] => *** 
    [subject] => ***
    [html] => ***
    [attachment] => Array
        (
            [0] => /home/***/n.jpg
            [1] => /home/***/n2.jpg
        )

)