code: func (c CookieOptions) deleteCookie(w http.ResponseWriter) {
  	cookie := &http.Cookie{
  		// If the browser refuses to delete it, set value to "" so subsequent
  		// requests replace it when it does not point to a valid session id.
  		Path:     c.Path,
  		Domain:   c.Domain,
  		Value:    "",
  		Name:     c.Name,
  		MaxAge:   -1,
  		Expires:  time.Now().UTC().AddDate(-1, 0, 0),
  		HttpOnly: c.HTTPOnly,
  		Secure:   c.Secure,
  	}
  
  	w.(cookieWriter).SetCookie(cookie)
  }
docs: // deleteCookie sets the cookie to a deleted value to force the client to delete