Fiber: 🐛 logger middleware doesn't work well with etag

[dhcmrlchtdj]

Fiber version
v2.0.6

Issue description
curl -v http://localhost:3000 -H 'If-None-Match: "9-450763418"' return 304 Not Modified with empty body.
but logger print GET / | status: 200 | bytesSent: 9, the status and bytesSent are wrong.

Code snippet

package main

import (
    "github.com/gofiber/fiber/v2"
    "github.com/gofiber/fiber/v2/middleware/logger"
)

func main() {
    app := fiber.New(fiber.Config{ETag: true})

    app.Use(logger.New(logger.Config{
        Format: "${method} ${path} | status: ${status} | bytesSent: ${bytesSent}\n",
    }))
    app.Get("/", func(c *fiber.Ctx) error {
        return c.SendString("with etag")
    })

    app.Listen(":3000")
}

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[dhcmrlchtdj]

a possible sulotion
export etag functionality as a middleware, which can be mounted after logger middleware.
for compatibility, we can mount etag middleware inside app.Listen, and add a deprecate warning to etag option.

[kiyonlin]

a possible sulotion

export etag functionality as a middleware, which can be mounted after logger middleware.

for compatibility, we can mount etag middleware inside app.Listen, and add a deprecate warning to etag option.

@dhcmrlchtdj Maybe we can use etag option to determine whether we should hit etag middleware

[dhcmrlchtdj]

for compatibility, we can mount etag middleware inside app.Listen

hmm, it is infeasible.

package github.com/gofiber/fiber/v2
    imports github.com/gofiber/fiber/v2/middleware/etag
    imports github.com/gofiber/fiber/v2: import cycle not allowed

[kiyonlin]

etag middleware should be placed in fiber core folder.

[dhcmrlchtdj]

I encounter some difficulties.

etag middleware should be mounted at a special time.

1. after logger middleware, otherwise logger maybe print incorrect status code.
2. before user handlers, otherwise the etag middleware doesn't invoked.

app.Listen does not satisfied the requirements.

[Fenny]

Thanks @dhcmrlchtdj for this bug report, the idea to add the ETag logic as a middleware to provide more flexibility was spot on.
https://github.com/gofiber/fiber/pull/926 will be tagged in version v2.1.0 and should solve this problem, I will leave this issue open until it's released 👍

[Fenny]

ETag middleware is now available in v2.1.0, you can place this mw after the logger 👍

package main

import (
    "github.com/gofiber/fiber/v2"
    "github.com/gofiber/fiber/v2/middleware/etag"
    "github.com/gofiber/fiber/v2/middleware/logger"

)

func main() {
    app := fiber.New()

    app.Use(logger.New())
    app.Use(etag.New())

    app.Get("/", func(c *fiber.Ctx) error {
        return c.SendString("with etag")
    })

    app.Listen(":3000")
}