fiberresp

fiberresp

A standardized response handling package for Fiber web framework with i18n support.

Features

• Standardized JSON response format
• Internationalization (i18n) support
• Customizable error codes and messages
• Fluent interface for building responses
• Support for status codes, causes, and localization parameters

Installation

go get github.com/prongbang/fiberresp

Usage

Basic Usage

import (
    "github.com/gofiber/fiber/v2"
    "github.com/prongbang/fiberresp"
    "net/http"
)

func handler(c *fiber.Ctx) error {
    err := fiberresp.New("ERR001", "errors.not_found")
    return fiberresp.With(c).Response(err)
}

Setting Up i18n

Configure i18n in your Fiber application:

import (
    "github.com/gofiber/contrib/fiberi18n/v2"
    "github.com/gofiber/fiber/v2"
    "golang.org/x/text/language"
)

func main() {
    app := fiber.New()
    app.Use(fiberi18n.New(&fiberi18n.Config{
        RootPath:         "./localize",
        FormatBundleFile: "json",
        AcceptLanguages:  []language.Tag{language.Thai, language.English},
        DefaultLanguage:  language.English,
    }))

    // Routes
    // ...
}

Predefined Error Responses

Create reusable error responses:

func NewBadRequest() *fiberresp.ResponseBody {
    return &fiberresp.ResponseBody{
        Code:         "CLT001",
        Message:      "errors.bad_request",
        StatusCode:   http.StatusBadRequest,
        LocaleParams: make(map[string]any),
    }
}

func NewNotFound() *fiberresp.ResponseBody {
    return &fiberresp.ResponseBody{
        Code:         "CLT002",
        Message:      "errors.not_found",
        StatusCode:   http.StatusNotFound,
        LocaleParams: make(map[string]any),
    }
}

func NewUnauthorized() *fiberresp.ResponseBody {
    return &fiberresp.ResponseBody{
        Code:         "AUT001",
        Message:      "errors.unauthorized",
        StatusCode:   http.StatusUnauthorized,
        LocaleParams: make(map[string]any),
    }
}

func NewFieldRequired() *fiberresp.ResponseBody {
    return &fiberresp.ResponseBody{
        Code:       "VAL001",
        Message:    "validation.field.required",
        StatusCode: http.StatusBadRequest,
        LocaleParams: map[string]any{
            "field": "username",
        },
    }
}

Using Localization Parameters

Add dynamic parameters to error messages:

// Field validation example
app.Get("/validate-email", func(c *fiber.Ctx) error {
    err := fiberresp.New("VAL001", "validation.field.required").
        WithParam("field", "email")
    return fiberresp.With(c).Response(err)
})

// Length validation example
app.Get("/validate-username", func(c *fiber.Ctx) error {
    err := fiberresp.New("VAL002", "validation.username.length").
        WithParam("min", 3).
        WithParam("max", 20)
    return fiberresp.With(c).Response(err)
})

Complete Example

package main

import (
    "github.com/gofiber/contrib/fiberi18n/v2"
    "github.com/gofiber/fiber/v2"
    "github.com/gofiber/fiber/v2/log"
    "github.com/prongbang/fiberresp"
    "golang.org/x/text/language"
    "net/http"
)

func main() {
    app := fiber.New()
    app.Use(fiberi18n.New(&fiberi18n.Config{
        RootPath:         "./localize",
        FormatBundleFile: "json",
        AcceptLanguages:  []language.Tag{language.Thai, language.English},
        DefaultLanguage:  language.English,
    }))

    app.Get("/test-bad-request", func(c *fiber.Ctx) error {
        return fiberresp.With(c).Response(NewBadRequest())
    })

	app.Get("/test-username-required", func(c *fiber.Ctx) error {
		return fiberresp.With(c).Response(NewFieldRequired())
	})

    app.Get("/test-email-required", func(c *fiber.Ctx) error {
        err := fiberresp.New("VAL001", "validation.field.required").
            WithParam("field", "email")
        return fiberresp.With(c).Response(err)
    })

    log.Fatal(app.Listen(":3000"))
}

func NewBadRequest() *fiberresp.ResponseBody {
    return &fiberresp.ResponseBody{
        Code:         "CLT001",
        Message:      "errors.bad_request",
        StatusCode:   http.StatusBadRequest,
        LocaleParams: make(map[string]any),
    }
}

func NewFieldRequired() *fiberresp.ResponseBody {
	return &fiberresp.ResponseBody{
		Code:       "VAL001",
		Message:    "validation.field.required",
		StatusCode: http.StatusBadRequest,
		LocaleParams: map[string]any{
			"field": "username",
		},
	}
}

Localization Example

Example of localization JSON files:

./localize/en.json:

{
  "errors.bad_request": "Bad Request",
  "errors.not_found": "Not Found",
  "errors.unauthorized": "Unauthorized",
  "validation.field.required": "The {{.field}} field is required",
  "validation.username.invalid": "Invalid username",
  "validation.username.length": "Username must be between {{.min}} and {{.max}} characters"
}

./localize/th.json:

{
  "errors.bad_request": "คำขอไม่ถูกต้อง",
  "errors.not_found": "ไม่พบข้อมูล",
  "errors.unauthorized": "ไม่มีสิทธิ์เข้าถึง",
  "validation.field.required": "กรุณากรอกข้อมูล {{.field}}",
  "validation.username.invalid": "ชื่อผู้ใช้ไม่ถูกต้อง",
  "validation.username.length": "ชื่อผู้ใช้ต้องมีความยาวระหว่าง {{.min}} ถึง {{.max}} ตัวอักษร"
}

Response Structure

The JSON response format:

{
  "code": "ERR001",
  "message": "Not Found",
  "data": null,
  "cause": "Optional error cause"
}

API Reference

ResponseBody

type ResponseBody struct {
    Code         string         `json:"code"`
    Data         any            `json:"data"`
    Message      string         `json:"message"`
    Cause        *string        `json:"cause,omitempty"`
    StatusCode   int            `json:"-"`
    LocaleParams map[string]any `json:"-"`
}

Methods

• New(code string, message string) *ResponseBody: Create a new error response
• WithData(data any) *ResponseBody: Set response data
• WithStatusCode(statusCode int) *ResponseBody: Set HTTP status code
• WithCause(cause string) *ResponseBody: Set error cause
• WithMessage(message string) *ResponseBody: Set error message
• WithParams(params map[string]any) *ResponseBody: Set multiple localization parameters
• WithParam(key string, value any) *ResponseBody: Set a single localization parameter
• With(ctx *fiber.Ctx) *Config: Initialize response with Fiber context
• Response(err *ResponseBody) error: Send response to client

License

MIT