Missing code challenge about gin-server HOT 3 OPEN

func (m *Manager) validateCodeChallenge(ti oauth2.TokenInfo, ver string) error {
	cc := ti.GetCodeChallenge()
	// early return
	if cc == "" && ver == "" {
		return nil
	}
	if cc == "" {
		return errors.ErrMissingCodeVerifier
	}
	if ver == "" {
		return errors.ErrMissingCodeVerifier
	}
	ccm := ti.GetCodeChallengeMethod()
	if ccm.String() == "" {
		ccm = oauth2.CodeChallengePlain
	}
	if !ccm.Validate(cc, ver) {
		return errors.ErrInvalidCodeChallenge
	}
	return nil
}