code: func (evc ExternalEtcdVersionCheck) configCertAndKey(config *tls.Config) (*tls.Config, error) {
  	var cert tls.Certificate
  	if evc.Etcd.External.CertFile != "" && evc.Etcd.External.KeyFile != "" {
  		var err error
  		cert, err = tls.LoadX509KeyPair(evc.Etcd.External.CertFile, evc.Etcd.External.KeyFile)
  		if err != nil {
  			return nil, errors.Wrapf(err, "couldn't load external etcd's certificate and key pair %s, %s", evc.Etcd.External.CertFile, evc.Etcd.External.KeyFile)
  		}
  		if config == nil {
  			config = &tls.Config{}
  		}
  		config.Certificates = []tls.Certificate{cert}
  	}
  	return config, nil
  }
docs: // configCertAndKey configures and returns a reference to tls.Config instance if CertFile and KeyFile pair is provided