m.Use(captcha.Captchaer(captcha.Options{
// URL prefix of getting captcha pictures. Default is "/captcha/".
// Hidden input element ID. Default is "captcha_id".
FieldIdName: "captcha_id",
// User input value element name in request form. Default is "captcha".
FieldCaptchaName: "captcha",
// Challenge number. Default is 6.
// Captcha image width. Default is 240.
// Captcha image height. Default is 80.
// Captcha expiration time in seconds. Default is 600.
// Cache key prefix captcha characters. Default is "captcha_".