auth0.go
func NewValidator(config Configuration, extractor RequestTokenExtractor) *JWTValidator {
	if extractor == nil {
		extractor = RequestTokenExtractorFunc(FromHeader)
	}
	return &JWTValidator{config, extractor}
}
func NewValidator(config Configuration, extractor RequestTokenExtractor) *JWTValidator {
	if extractor == nil {
		extractor = RequestTokenExtractorFunc(FromHeader)
	}
	return &JWTValidator{config, extractor}
}
// NewValidator creates a new
// validator with the provided configuration.