// AddSignedCookie adds the specified cookie to the response and also adds an
// additional 'signed' cookie that is used to validate the cookies value when
// SignedCookie is called.
func (c *Context) AddSignedCookie(cookie *http.Cookie) (*http.Cookie, error) {

	// make the signed cookie
	signedCookie := new(http.Cookie)

	// copy the cookie settings
	signedCookie.Path = cookie.Path
	signedCookie.Domain = cookie.Domain
	signedCookie.RawExpires = cookie.RawExpires
	signedCookie.Expires = cookie.Expires
	signedCookie.MaxAge = cookie.MaxAge
	signedCookie.Secure = cookie.Secure
	signedCookie.HttpOnly = cookie.HttpOnly
	signedCookie.Raw = cookie.Raw

	// set the signed cookie specifics
	signedCookie.Name = toSignedCookieName(cookie.Name)
	signedCookie.Value = Hash(cookie.Value)

	// add the cookies
	http.SetCookie(c.ResponseWriter, cookie)
	http.SetCookie(c.ResponseWriter, signedCookie)

	// return the new signed cookie (and no error)
	return signedCookie, nil

}