Go-validator custom error message (option 1)

go-validator.go

// Usage, in controller or validate struct
  err := ctx.ShouldBindJSON(&request)
	if err != nil {
		for _, fieldErr := range err.(validator.ValidationErrors) {
			fmt.Println("error", fieldErr)
			vgin.BuildErrorResponse(ctx, verrors.NewInvalidRequestFormatError(errors.New(validation.FieldError{fieldErr}.String())))

			return // exit on first error
		}
  }

// Convert tag name from StructKey to JSON tag.
// Exp: IDType to id_type
// Put before initGin
func RegisterTagNameJSON() {
	validate := binding.Validator.Engine().(*validator.Validate)

	validate.RegisterTagNameFunc(func(fld reflect.StructField) string {
		name := strings.SplitN(fld.Tag.Get("json"), ",", 2)[0]
		if name == "-" {
			return ""
		}
		return name
	})
}



// Validatation
type FieldError struct {
	Err validator.FieldError
}

func (q FieldError) String() string {
	var sb strings.Builder
	a(q.Err)
	sb.WriteString("field '" + q.Err.Field() + "'")
	sb.WriteString(", condition: " + q.Err.Tag())

	// Print condition parameters, e.g. oneof=red blue -> { red blue }
	if q.Err.Param() != "" {
		sb.WriteString(" { " + q.Err.Param() + " }")
	}

	if q.Err.Value() != nil && q.Err.Value() != "" {
		sb.WriteString(fmt.Sprintf(", actual: %v", q.Err.Value()))
	}

	return sb.String()
}