Empty done channel makes ctx always done when creating test server

[quagmt]

Description

• I'm using fiber, which uses fasthttp v1.57. I think the recent changes in server.done channel initialization causes the context to always done when writing tests. Considering this example:

package main

import (
	"context"
	"io"
	"net/http"

	"github.com/gofiber/fiber/v2"
)

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

	app.Get("/", func(c *fiber.Ctx) error {
		select {
		case <-c.Context().Done():
			return c.JSON("context is done")
		default:
			return c.JSON("context is not done")
		}
	})

	req, _ := http.NewRequestWithContext(context.Background(), "GET", "/", nil)
	resp, _ := app.Test(req)

	defer resp.Body.Close()

	body, _ := io.ReadAll(resp.Body)

	// Output: should be "context is not done" but it's "context is done"
	println(string(body))
}

• The reason I think is that server.done channel is only initialized when calling server.Serve or when checking context.Done(). Its value is nil when creating a new fasthttp.Server struct, which fiber v2 is doing.
• c.Context().Done() will create a new channel (because done is nil) and send an empty message to the channel, which causes the context.Done() to return immediately. (though I'm not sure if this is intentional).
• done channel is also not exported so it's impossible to assign it to a channel to avoid this issue. I see there's a fakeServer which init the done channel, but it's also not exported. Is this possible to have a method to init this done channel?

EDIT: this doesn't happen if we run the server and serve real requests because done channel is created when calling server.Serve