Learning Go: How to use http.HandlerFunc?

Trying To Learn Go

My Test Project

I am building a simple API to communicate with a light SQL database.
I created this function, that gets all hosts from the DB table.
As I understand, my function should take a pointer to the DB and return me http.HandlerFunc.

func (h HostController) GetAllHosts(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var host entities.Host
		var hosts []entities.Host
		var errorMessage entities.Error
		rows, err := db.Query("SELECT * FROM hosts WHERE hosts = ?", host)
		if err != nil {
			errorMessage.Message = "Error: Get all hosts"
			utils.SendError(w, http.StatusInternalServerError, errorMessage)
			return
		}
		defer rows.Close()
		for rows.Next() {
			err := rows.Scan(&host.ID, &host.Uuid, &host.Name, &host.IPAddress)
			if err != nil {
				errorMessage.Message = "Error: (Get all hosts) Can't scan rows"
				utils.SendError(w, http.StatusInternalServerError, errorMessage)
				return
			}
			hosts = append(hosts, host)
		}
		////If hosts slice is empty -> no data in database
		if len(hosts) == 0 {
			errorMessage.Message = "No found hosts in database"
			utils.SendError(w, http.StatusInternalServerError, errorMessage)
			return
		}
		//Convert containers content to JSON representation
		w.Header().Set("Content-Type", "application/json")
		utils.SendSuccess(w, hosts)
	}
}

Now, Until here everything should be good, but I don't know how to implement this on main.go
build layout:

.
├── controllers
│       └── hostcontroller.go
│       
└── main.go

and this is how I am trying to implement it on the main.go

package main

import (
	"examProg/config"
	"examProg/controllers"
	"fmt"
	"log"
	"net/http"

	"github.com/gorilla/mux"
	_ "github.com/mattn/go-sqlite3"
)

func main() {
	db := config.GetDB() //Establishing connection to DBase
	{

		router := mux.NewRouter()

		router.Handle("/host", controllers.HostController.GetAllHosts(db))

		fmt.Println("Server is running at port: 2030")
		log.Println("Server Running OK | Port: 2030")
		log.Fatal(http.ListenAndServe(":2030", router))
	}

}

I don't understand how to implement the http.HandlerFunc 🙃

The expression controllers.HostController.GetAllHosts is a method expression. The result of a method expression is a function that, in addition to the method's argument's, takes an instance of the receiver's type as its first argument.

Hence the "not enough arguments in call ..." error.

To illustrate:

f := controllers.HostController.GetAllHosts
fmt.Println(reflect.TypeOf(f))
// output: func(controllers.HostController, *sql.DB)

So, to make the code compile, you need to pass an instance of controllers.HostController to the call, i.e.

controllers.HostController.GetAllHosts(controllers.HostController{}, db)

As you can see, it ain't pretty. Method expressions have their use, I'm sure, but I haven't encountered them much. What I see most often instead, is the use of method values.

h := controllers.HostController{}
router.Handle("/host", h.GetAllHosts(db))