code: func NewCookie(name, value string, options *Options) *http.Cookie {
  	cookie := newCookieFromOptions(name, value, options)
  	if options.MaxAge > 0 {
  		d := time.Duration(options.MaxAge) * time.Second
  		cookie.Expires = time.Now().Add(d)
  	} else if options.MaxAge < 0 {
  		// Set it to the past to expire now.
  		cookie.Expires = time.Unix(1, 0)
  	}
  	return cookie
  }
docs: // NewCookie returns an http.Cookie with the options set. It also sets
  // the Expires field calculated based on the MaxAge value, for Internet
  // Explorer compatibility.