Why does mux.Vars() returns empty map[]

I get an empty map[] from mux.Vars[].

After tracing the problem, it seems to be an empty map[] passed through my multiple files.

While in the same file: I have imported the other file as a module(I believe) in the import

package main

import(
"github.com/Ny0ttt/go-bookstore/pkg/controllers"
//note that this is imported from powershell, go mod init "github.com/Ny0ttt/go-bookstore"
)

while after running go run main.go, I obtain the map[] as map[ID]

While in a different file:

as per imported like the previous one, I receive an empty map[]

Here is my file structure

> Go-Test/cmd/main/main.exe
> Go-Test/cmd/main/main.go
> Go-Test/pkg/config/app.go
> Go-Test/pkg/models/models.go
> Go-Test/pkg/controllers/book-controller.go
> Go-Test/pkg/utils/utils.go
> Go-Test/go.sum
> Go-Test/go.mod

and my mod file contains

module github.com/Ny0ttt/go-bookstore

go 1.20

require (
	github.com/go-sql-driver/mysql v1.5.0
	github.com/gorilla/mux v1.8.0
	github.com/jinzhu/gorm v1.9.16
)

require github.com/jinzhu/inflection v1.0.0 // indirect

Here are my codes :

In my Controller

func GetBookById(w http.ResponseWriter, r *http.Request){
	vars := mux.Vars(r)
	bookId := vars["ID"]
	ID, err := strconv.ParseInt(bookId, 0, 0)
	if err != nil{
		fmt.Println("error while parsing")
		fmt.Println(r)
		fmt.Println(bookId)
		fmt.Println(vars)
	}
	bookDetails, _ := models.GetBookById(ID) //mthis model returns 2 variable but we will be using only one of them. refer models
	res, _ := json.Marshal(bookDetails)
	w.Header().Set("Content-Type","pkglication/json")
	w.WriteHeader(http.StatusOK)
	w.Write(res)
}

In my Routes

func main() {
	r := mux.NewRouter()
	
	//routes.RegisterBookStoreRoutes(r)
	r.HandleFunc("/book/", controllers.GetBook).Methods("GET")
	r.HandleFunc("/book/", controllers.CreateBook).Methods("POST")
	r.HandleFunc("/book/{ID}", controllers.GetBookById).Methods("GET")
	r.HandleFunc("/book/{bookId}", controllers.UpdateBook).Methods("PUT")
	r.HandleFunc("/book/{bookId}", controllers.DeleteBook).Methods("DELETE")
        http.Handle("/", r)
	log.Fatal(http.ListenAndServe(":2222", r)) // creating a server
}

The output

error while parsing
&{GET /book/1 HTTP/1.1 1 1 map[Accept:[*/*] Accept-Encoding:[gzip, deflate, br] Connection:[keep-alive] Postman-Token:[a28eebe1-b6d4-4aff-89ed-d3b93a4ed1df] User-Agent:[PostmanRuntime/7.32.3]] {} <nil> 0 [] false :2222 map[] map[] <nil> map[] 127.0.0.1:52035 /book/1 <nil> <nil> <nil> 0xc000282a20}

map[]

Note: I print out the values so I can trace where it did go wrong, *http.Request does not map any values? I am not sure what map[] in return http.Request should look like.

I looked up for solutions, but it seems like i need more explaination on those alternatives. I have look up on r.URL.Query but the problem that they are facing is when using a different route structure.

I have also looked up for another alternative with `mux.RouteMatch` but I think I could use a little bit of explanation.

Problem Solved

I simply moved my project into the desktop (I am sure you may move wherever you want as long as you don't need administrator power to access the directory ) and it works.

I will continue exploring projects in a accessible directory from now on. Thank you.