egg-cnode中有段代码不理解，请教下为什么要用for循环 https://github.com/cnodejs/egg-cnode/blob/master/app/service/mail.js#L18
代码
for (let i = 1; i < 6; i++) { try { await transporter.sendMail(data); logger.info('send mail success', data); break; } catch (err) { if (i === 5) { logger.error('send mail finally error', err, data); throw new Error(err); } logger.error('send mail error', err, data); } }