fiber

Fiber Best Practices

Fiber is a high-performance, Express-inspired web framework for Go, built on fasthttp. These rules ensure we leverage Fiber's speed and maintainability while avoiding common pitfalls.

1. Core Principle: fiber.Ctx Immutability

NEVER retain references to fiber.Ctx or any data extracted from it (like c.Params, c.Query, c.Body) after the handler returns. fiber.Ctx values are reused across requests, making their contents ephemeral. Always copy data if you need to store it.

❌ BAD: Retaining ephemeral data

package handlers

import (
	"github.com/gofiber/fiber/v2"
	"log"
)

// This struct will hold a reference to the ephemeral string
type UserRequest struct {
	UserID string
}

func GetUserBad(c *fiber.Ctx) error {
	// DANGER: c.Params("id") returns an ephemeral string.
	// Storing it directly will lead to data corruption in future requests.
	req := &UserRequest{
		UserID: c.Params("id"),
	}

	// Simulating async processing or storage
	go func() {
		// By the time this goroutine runs, c.Params("id") might have changed
		log.Printf("Processing user ID: %s", req.UserID) // Will likely be wrong
	}()

	return c.SendString("Request received (bad example)")
}

✅ GOOD: Copying ephemeral data

package handlers

import (
	"github.com/gofiber/fiber/v2"
	"github.com/gofiber/fiber/v2/utils" // Use Fiber's utility for efficient copying
	"log"
)

// This struct holds a safe copy of the string
type UserRequest struct {
	UserID string
}

func GetUserGood(c *fiber.Ctx) error {
	// ALWAYS copy data from c.Params, c.Query, c.Body, etc.
	userID := utils.CopyString(c.Params("id"))
	req := &UserRequest{
		UserID: userID,
	}

	// Simulating async processing or storage
	go func() {
		// This is safe; userID is a distinct copy
		log.Printf("Processing user ID: %s", req.UserID) // Will always be correct
	}()

	return c.SendString("Request received (good example)")
}

2. Code Organization and Structure

Organize your application into logical layers: main, config, router, middleware, handlers, services, repository, models, utils.