09-basic-server-sent-events

Server Sent Events

Server pushes updates to the client over a single HTTP connection

1. Set up the HTTP server:
   

http.ListenAndServe(":8000", nil)

2. Write the HTTP handler to send events:
   We send current timestamps, wrapped in fmt.Fprintf and flush the data.

SSEHandler(w http.ResponseWriter, r *http.Request)
    for {
		fmt.Fprintf(w, "data: Current time is %s\n\n", time.Now().Format(time.RFC3339))

		// flush the data to the client - immideately, not buffer
		if f, ok := w.(http.Flusher); ok {
			f.Flush()
		}
    }

3. Set up the client to listen to the events:
   

const eventSource = new EventSource("http://localhost:8080/events");

// Listen for messages from the server
eventSource.onmessage = function(event) {
    const newElement = document.createElement("div");
    newElement.textContent = event.data;
    document.getElementById("events").appendChild(newElement);
};

Result