Golang Redis websocket handler - go

Question

I need help with Golang websocket. I'm using Fiber with websocket and redis.
Here is the code:
package main
import (
"context"
"encoding/json"
"fmt"
"github.com/go-redis/redis/v8"
"github.com/gofiber/fiber/v2"
"github.com/gofiber/websocket/v2"
"log"
"test4/controllers"
)
type User struct {
Name string `json:"name"`
Email string `json:"email"`
}
var ctx = context.Background()
var redisClient = redis.NewClient(&redis.Options{
Addr: "localhost:6379",
})
func TestSocket() fiber.Handler {
socket := websocket.New(func(c *websocket.Conn) {
go deliverMessages(c)
var (
msg []byte
err error
)
for {
if _, msg, err = c.ReadMessage(); err != nil {
log.Println("read:", err)
break
}
if err := redisClient.Publish(ctx, "chat", msg).Err(); err != nil {
log.Println("publish:", err)
break
}
}
})
return socket
}
func deliverMessages(c *websocket.Conn) {
subscriber := redisClient.Subscribe(ctx, "chat")
user := User{}
for {
msg, err := subscriber.ReceiveMessage(ctx)
if err != nil {
log.Println("subscriber:", err)
panic(err)
}
if err := json.Unmarshal([]byte(msg.Payload), &user); err != nil {
log.Println("Unmarshal:", err)
panic(err)
}
text := []byte(fmt.Sprintf("{\"name\":\"%s\", \"email\":\"%s\"}", user.Name, user.Email))
if err = c.WriteMessage(websocket.TextMessage, text); err != nil {
log.Println("write:", err)
break
}
}
}
func main() {
app := fiber.New(fiber.Config{
Prefork: true,
CaseSensitive: true,
StrictRouting: true,
DisableStartupMessage: true,
ServerHeader: "Test v3",
})
app.Get("/", controllers.Home)
app.Get("/ws", TestSocket())
log.Fatal(app.Listen("0.0.0.0:3000"))
}
How to produce the error:
Install Redis and run go run main.go
Now open http://127.0.0.1:3000/ in two tabs
click open on both tabs, and then you will see OPEN on right side of browser
click send on both tabs and you will get SEND and RESPONSE
Now close one tab and on go program terminal you will see error (see attached screenshot)
Now publish data to chat channel on redis-cli
Here is the error I am getting:

Answer 1

I think this is nil pointer websocket.Conn issue.
When close websocket connection, goroutine's c *websocket.Conn is loose data.
Pointer point nil.
solution
use channel, use local redisClient var
func TestSocket() fiber.Handler {
socket := websocket.New(func(c *websocket.Conn) {
var redisClient = redis.NewClient(&redis.Options{ // <-- use local redisClient var
Addr: "localhost:6379",
})
go deliverMessages(c)
var (
msg []byte
err error
)
defer func() {
redisClient.Close() // <-- then close, when websocket connection close
quitSubscribeGoRutine <- true // <-- change true, when websocket connection close
}()
for {
if _, msg, err = c.ReadMessage(); err != nil {
log.Println("read:", err)
...
func deliverMessages(c *websocket.Conn) {
subscriber := redisClient.Subscribe(ctx, "chat")
user := User{}
for {
select {
case <-quitSubscribeGoRutine: // <-- exit goroutine, when channel is true
return
default:
msg, err := subscriber.ReceiveMessage(ctx) // <-- exit goroutine, when redisClient close
if err != nil {
log.Println("subscriber:", err)
break // <-- use break instead of panic
}
if err := json.Unmarshal([]byte(msg.Payload), &user); err != nil {
log.Println("Unmarshal:", err)
panic(err)
}
text := []byte(fmt.Sprintf("{\"name\":\"%s\", \"email\":\"%s\"}", user.Name, user.Email))
if err = c.WriteMessage(websocket.TextMessage, text); err != nil {
log.Println("write:", err)
break
}
}
}
}