fix: prevent concurrent write to websocket connection

- refactor client handling and message broadcasting
- replace Client struct
- implement SendMessage method in Client struct for safer message sending
- update client map to use *models.Client instead of bool
- adjust BroadcastMessage and RunPomodoroTimer functions to use new client type

🤖

pkg/models/broadcast.go

@@ -7,8 +7,3 @@ type BroadcastMessage struct {
 	MaxSession int    `json:"max_session"` // Total number of sessions
 	TimeLeft   int    `json:"time_left"`   // Remaining time in seconds
 }
-
-// ClientCommand represents a command from the client (start/stop).
-type ClientCommand struct {
-	Command string `json:"command"`
-}

pkg/models/client.go

@@ -0,0 +1,30 @@
+package models
+
+import (
+	"github.com/gorilla/websocket"
+	"log"
+	"sync"
+)
+
+// ClientCommand represents a command from the client (start/stop).
+type ClientCommand struct {
+	Command string `json:"command"`
+}
+
+type Client struct {
+	Conn  *websocket.Conn
+	Mutex sync.Mutex
+}
+
+// It automatically locks and unlocks the mutex to ensure that only one goroutine can write at a time.
+func (c *Client) SendMessage(messageType int, data []byte) error {
+	c.Mutex.Lock()
+	defer c.Mutex.Unlock()
+
+	err := c.Conn.WriteMessage(messageType, data)
+	if err != nil {
+		log.Printf("Error writing to WebSocket: %v", err)
+		c.Conn.Close() // Close the connection on error
+	}
+	return err
+}