Golang RCP call hanging

I have a back-end app and a front-end, both in Go. I am trying to make them talk via rpc.

back-end main.go

package main
import (
"fmt"
"log"
"net"
"net/http"
"net/rpc"
"time"
)
type Application struct {
config struct {
server struct {
port    int
network string
}
}
}
type MusicProject struct {
Id             string
CreatedTime    time.Time
LastEditedTime time.Time
Title          string
Year           int
Status         string
Description    string
ChoirRollup    string
}
func main() {
var app Application
app.config.server.port = 5002
app.config.server.network = "tcp"
if err := rpc.Register(new(Application)); err != nil {
log.Fatal(err)
}
rpc.HandleHTTP()
// start the rpc server
log.Println("Starting server port", app.config.server.port)
l, err := net.Listen("tcp", fmt.Sprintf(":%v", app.config.server.port))
if err != nil {
log.Fatal(err)
}
if err = http.Serve(l, nil); err != nil {
log.Fatal(err)
}
}
func (app *Application) GetMusicProjectById(id string, model *MusicProject) error {
musicProject := MusicProject{
Id:             id,
CreatedTime:    time.Now(),
LastEditedTime: time.Now(),
Title:          "Test Project",
Year:           2020,
Status:         "Completed",
Description:    "Short project Description",
ChoirRollup:    "Best Choir",
}
model = &musicProject
return nil
}

front-end rpc call

package main
import (
"log"
"net/rpc"
"time"
)
type MusicProject struct {
Id             string
CreatedTime    time.Time
LastEditedTime time.Time
Title          string
Year           int
Status         string
Description    string
ChoirRollup    string
}
func main() {
dial, err := rpc.Dial("tcp", "localhost:5002")
if err != nil {
log.Println(err)
}
projectID := "some_id_123"
var musicProject MusicProject
err = dial.Call("Application.GetMusicProjectById", projectID, &musicProject)
if err != nil {
log.Println(err)
}
log.Println(musicProject)
}

Once the client method is call, the call hanged indefinite with out sending back any error, so quite difficult to debug.

Do you have any suggestion for debugging? Do you see anything wrong in my code?
Thank you for your help!

Your server is serving HTTP:

if err = http.Serve(l, nil); err != nil {
   log.Fatal(err)
}

But your client is using straight TCP (HTTP runs over TCP but adds another layer):

err = dial.Call("Application.GetMusicProjectById", projectID, &musicProject)

So to fix your issue you need to change one side or the other. For example change the server to:

rpc.Accept(l)

(alternatively you could use rpc.DialHTTP in the client)

There are a couple of other issues with your code (the main one being the way you set the response in the back-end). The following works for me (have not put much effort into making it tidy or testing!).

server

package main

import (
	"fmt"
	"log"
	"net"
	"net/rpc"
	"time"
)

type MusicProject struct {
	Id             string
	CreatedTime    time.Time
	LastEditedTime time.Time
	Title          string
	Year           int
	Status         string
	Description    string
	ChoirRollup    string
}

type Application struct {
}

func (app *Application) GetMusicProjectById(id string, model *MusicProject) error {
	*model = MusicProject{
		Id:             id,
		CreatedTime:    time.Now(),
		LastEditedTime: time.Now(),
		Title:          "Test Project",
		Year:           2020,
		Status:         "Completed",
		Description:    "Short project Description",
		ChoirRollup:    "Best Choir",
	}
	return nil
}

func main() {
	const port = 5002
	if err := rpc.Register(new(Application)); err != nil {
		log.Fatal(err)
	}

	// start the rpc server
	log.Println("Starting server on port:", port)
	l, err := net.Listen("tcp", fmt.Sprintf(":%d", port))
	if err != nil {
		log.Fatal(err)
	}
	rpc.Accept(l)
}

client

package main

import (
	"log"
	"net/rpc"
	"time"
)

type MusicProject struct {
	Id             string
	CreatedTime    time.Time
	LastEditedTime time.Time
	Title          string
	Year           int
	Status         string
	Description    string
	ChoirRollup    string
}

func main() {
	dial, err := rpc.Dial("tcp", "localhost:5002")
	if err != nil {
		log.Fatal(err)
	}

	projectID := "some_id_123"

	var musicProject MusicProject

	err = dial.Call("Application.GetMusicProjectById", projectID, &musicProject)
	if err != nil {
		log.Fatal("error:", err)
	}
	log.Println(musicProject)
}