code: func (c *Challenge) Delete(w http.ResponseWriter, r *http.Request) error {
  	session, err := c.idp.config.ChallengeStore.Get(r, SessionCookieName)
  	if err != nil {
  		return err
  	}
  
  	session.Options = c.idp.deleteChallengeCookieOptions
  	return c.idp.config.ChallengeStore.Save(r, w, session)
  }
docs: // Deletes the challenge from the store