refactor: support request cancellation in SSE

that's my first use of select on channels, yay

routes/room_page.go

@@ -37,17 +37,23 @@ func streamingBsRoute() http.HandlerFunc {
 		w.Header().Set("Content-Type", "text/event-stream")
 		startTime, endTime := 0, 0
 		for {
+			select {
+			case <-r.Context().Done():
+				log.Printf("canlecced streaming!")
+				return
+			default:
 				log.Printf("another step in streaming bs")
 				data := "data: <div>hello with data %d! waited %d</div> \n\n"
 				startTime = time.Now().Nanosecond()
 				diff := endTime - startTime
 				fmt.Fprintf(w, data, rand.Intn(100), diff)
 				w.(http.Flusher).Flush()
-			time.Sleep(10 * time.Second)
+				time.Sleep(3 * time.Second)
 				endTime = time.Now().Nanosecond()
 			}
 		}
 	}
+}
 
 func roomPageRoute(
 	templateFs *embed.FS,