On the trial of the issue of the truth of the alleged attachment grounds, the defendant may introduce evidence as to the actual damages, if any, which the issuance of the attachment has occasioned him; but the defendant, when he files his answer setting up the defense traversing the truth of the alleged attachment grounds, shall file therewith written notice of what damages he will insist upon at the trial. If the issue be decided for the defendant, he shall have judgment that the attachment be discharged and against plaintiff and the sureties in his attachment bond, for the damages assessed by the jury and the costs of suit; and the jury may add to the actual damages found a reasonable sum as an attorney's fee for defending the issue; but the judgment against the sureties in the attachment bond shall not exceed the penalty thereof.