How to set Routes Group in Go Fiber V2 from separated file?

I want to make seperate files for each sub main routes. I am using go 1.17

main.go

package main

import (
	"rolling_glory_go/routes"

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

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

	app.Get("/", func(c *fiber.Ctx) error {
		err := c.SendString("Hello golang!")
		return err
	})

	routes.R_login(app.Group("/login"))
	routes.R_users(app.Group("/users"))

	app.Listen(":3000")
}

I want to import routes from r_login.go and r_users.go so i could manage many routes from different files and not put many routes from single file in main.go. I got an error like this.

.\main.go:17:26: cannot use app.Group("/login") (type fiber.Router) as type *fiber.Group in argument to routes.R_login: need type assertion
.\main.go:18:26: cannot use app.Group("/users") (type fiber.Router) as type *fiber.Group in argument to routes.R_users: need type assertion

My Structure Folder

r_login.go

package routes

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

func R_login(router *fiber.Group) {
	router.Get("/", func(c *fiber.Ctx) error {
		return c.SendString("respond with a resource")
	})
}

r_users.go

package routes

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

func R_users(router *fiber.Group) {
	router.Get("/", func(c *fiber.Ctx) error {
		return c.SendString("respond with a resource")
	})
}

How to fix this ?

As you have app.Group("/login") which of type fiber.Router
, just modify R_login to have it accept this type.

package routes

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

func R_login(router fiber.Router) {
    router.Get("/", func(c *fiber.Ctx) error {
        return c.SendString("respond with a resource")
    })
}

if anyone is still having issues I'm doing this in fiber/v2

func BookRouter(router fiber.Router) {
	router.Get("/", GetBook)
	router.Get("/all", GetBooks)
	router.Post("/", NewBook)
	router.Delete("/", DeleteBook)
}
 
	books := app.Group("/book")  //server.go
	books.Route("/", book.BookRouter)