refactor: support request cancellation in SSE

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

routes/room_page.go

@@ -37,14 +37,20 @@ func streamingBsRoute() http.HandlerFunc {
 		w.Header().Set("Content-Type", "text/event-stream")
 		startTime, endTime := 0, 0
 		for {
-			log.Printf("another step in streaming bs")
+			select {
-			data := "data: <div>hello with data %d! waited %d</div> \n\n"
+			case <-r.Context().Done():
-			startTime = time.Now().Nanosecond()
+				log.Printf("canlecced streaming!")
-			diff := endTime - startTime
+				return
-			fmt.Fprintf(w, data, rand.Intn(100), diff)
+			default:
-			w.(http.Flusher).Flush()
+				log.Printf("another step in streaming bs")
-			time.Sleep(10 * time.Second)
+				data := "data: <div>hello with data %d! waited %d</div> \n\n"
-			endTime = time.Now().Nanosecond()
+				startTime = time.Now().Nanosecond()
+				diff := endTime - startTime
+				fmt.Fprintf(w, data, rand.Intn(100), diff)
+				w.(http.Flusher).Flush()
+				time.Sleep(3 * time.Second)
+				endTime = time.Now().Nanosecond()
+			}
 		}
 	}
 }