go websocket

WebSockets are a protocol that provides a bi-directional, full-duplex communication channel over a single TCP connection. They enable real-time, low-latency communication between a client (usually a web browser) and a server.

To use WebSockets in a Go application, you can use the `gorilla/websocket` package. Here's an example of how to set up a WebSocket server:

package main

import (
	"log"
	"net/http"

	"github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
}

func main() {
	http.HandleFunc("/ws", handleWebSocket)
	log.Fatal(http.ListenAndServe(":8080", nil))
}

func handleWebSocket(w http.ResponseWriter, r *http.Request) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println("error upgrading to WebSocket:", err)
		return
	}
	defer conn.Close()

	for {
		// Read message from client
		_, message, err := conn.ReadMessage()
		if err != nil {
			log.Println("error reading message:", err)
			break
		}

		// Echo message back to client
		err = conn.WriteMessage(websocket.TextMessage, message)
		if err != nil {
			log.Println("error writing message:", err)
			break
		}
	}
}

In this example, we first set up an `upgrader` that will upgrade an HTTP connection to a WebSocket connection. We then define a `handleWebSocket` function that will handle WebSocket connections. Inside this function, we upgrade the connection using the `upgrader`, and then enter a loop to read messages from the client and echo them back.

To connect to this WebSocket server from a web browser, you can use JavaScript and the `WebSocket` API:

const ws = new WebSocket("ws://localhost:8080/ws");

ws.addEventListener("open", () => {
  console.log("Connected to WebSocket server");
});

ws.addEventListener("message", (event) => {
  console.log("Received message from server:", event.data);
});

ws.addEventListener("close", () => {
  console.log("Disconnected from WebSocket server");
});

ws.send("Hello, server!");

In this example, we create a new `WebSocket` object and connect to the server at `ws://localhost:8080/ws`. We then set up event listeners for the `open`, `message`, and `close` events. When the connection is opened, we log a message to the console. When a message is received from the server, we log it to the console. When the connection is closed, we log a message to the console. Finally, we send a message to the server using the `send` method.