form.go
func (f *FormErrors) AddFieldError(field, e string) {
	if f.FieldErrors == nil {
		f.FieldErrors = map[string][]string{}
	}
	if _, ok := f.FieldErrors[field]; !ok {
		f.FieldErrors[field] = []string{}
	}
	f.FieldErrors[field] = append(f.FieldErrors[field], e)
}
func (f *FormErrors) AddFieldError(field, e string) {
	if f.FieldErrors == nil {
		f.FieldErrors = map[string][]string{}
	}
	if _, ok := f.FieldErrors[field]; !ok {
		f.FieldErrors[field] = []string{}
	}
	f.FieldErrors[field] = append(f.FieldErrors[field], e)
}
// AddFieldError appends an error to a list of field specific errors.