func (e ValidationError) Error() string {
	if e.Inner != nil {
		return e.Inner.Error()
	} else if e.text != "" {
		return e.text
	} else {
		return "token is invalid"
	}
	return e.Inner.Error()
}
Validation error is an error type
package jwt
import (
	"errors"
)
var (
	ErrInvalidKey      = errors.New("key is invalid")
	ErrInvalidKeyType  = errors.New("key is of invalid type")
	ErrHashUnavailable = errors.New("the requested hash function is unavailable")
)
const (
	ValidationErrorMalformed        uint32 = 1 << iota  
	ValidationErrorUnverifiable                         
	ValidationErrorSignatureInvalid                     
	ValidationErrorAudience       
	ValidationErrorExpired        
	ValidationErrorIssuedAt       
	ValidationErrorIssuer         
	ValidationErrorNotValidYet    
	ValidationErrorId             
	ValidationErrorClaimsInvalid  
)
func NewValidationError(errorText string, errorFlags uint32) *ValidationError {
	return &ValidationError{
		text:   errorText,
		Errors: errorFlags,
	}
}
type ValidationError struct {
	Inner  error   
	Errors uint32  
	text   string  
}