To see the sample in action, run:
text
$ go run <path/to/server.go>
This starts up the server; it immediately reports which port it's listening on (the port can be changed with the -port flag).
Then open a browser and visit http://localhost:<portnum> to see the HTML page that talks with the server using websockets. The server also spins up a net/trace debugging page on /debug/requests.
The JavaScript code powering the served web page records mouse movement events over the shown box and sends them to the server through a websocket. The server echoes the data back and this is used to update the text reporting the coordinates.
Moreover, the server also periodically sends the current time over another websocket, which the client uses to update the time ticker at the top of the page.
For more details just check out the source - it's very simple.
This code is in the public domain. See the LICENSE file for more details.