Gorilla websocket very slow when more than one client using it

Question

I made a small chatting application using gorilla websocket. When there is only one client, it's fast, as expected. But when I connect with another client, the chat takes maybe 3 seconds to update, even when hosted on my local machine.

Code for websocket:

var clients = make(map[*websocket.Conn]bool)
var broadcast = make(chan Message)
var upgrader = websocket.Upgrader{}
func main() {
    router.HandleFunc("/ws", handleConnections)
    err := http.ListenAndServe(":80", router)
}
func handleConnections(w http.ResponseWriter, r *http.Request) {
    ws, err := upgrader.Upgrade(w, r, nil)
    if err != nil {
        log.Fatal(err)
    }
    defer ws.Close()
    clients[ws] = true
    for {
        var msg Message
        err := ws.ReadJSON(&msg)
        if err != nil {
            log.Printf("error: %v", err)
            delete(clients, ws)
            break
        }
        broadcast <- msg
    }
}

func handleMessages() {
    for {
        msg := <-broadcast
        log.Println(msg)
        database, _ := sql.Open("sqlite3", "./database.db")
        statement, _ := database.Prepare("CREATE TABLE IF NOT EXISTS messages (id INTEGER PRIMARY KEY, username TEXT, message TEXT, timestamp INTEGER)")
        statement.Exec()
        statement, _ = database.Prepare("INSERT INTO messages (username, message, timestamp) VALUES (?, ?, ?)")
        statement.Exec(&msg.Username, &msg.Message, &msg.Timestamp)
        for client := range clients {
            err := client.WriteJSON(msg)
            if err != nil {
                log.Printf("error: %v", err)
                client.Close()
                delete(clients, client)
            }
        }
    }
}

Full code: https://github.com/mismaah-abdulla/Chatapp-Backend/blob/de8cc0eb88fa7f18b293bb0f2229368887c53adf/src/main.go

Answer 1

The problem was that the database was locked when trying to write. The fix is simple adding defer rows.Close() everytime a query was run. For example:

func messages(w http.ResponseWriter, r *http.Request) {
    rows, _ := database.Query("SELECT username, message, timestamp FROM messages")
    defer rows.Close()
    var messages []Message
    for rows.Next() {
        var msg Message
        rows.Scan(&msg.Username, &msg.Message, &msg.Timestamp)
        messages = append(messages, msg)
    }
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(messages)
}