Server-Sent Events

Return dygo.SSE(seq) from a handler to stream text/event-stream. Each value is JSON encoded, and strings are sent as they are. Yield a dygo.SSEEvent to set the event’s ID, Event name or Retry time.

func (c *PricesController) Stream(ctx context.Context) (dygo.Responder, error) {
  prices := []Price{{"DYG", 1.5}, {"DYG", 1.6}}
  return dygo.SSE(iter.Seq[any](func(yield func(any) bool) {
    for i, p := range prices {
      ev := dygo.SSEEvent{ID: strconv.Itoa(i + 1), Event: "price", Data: p, Retry: 3 * time.Second}
      if !yield(ev) {
        return // the client went away
      }
    }
    yield("done") // a plain value is sent as a data-only event
  })), nil
}

The stream ends when the sequence ends, the client disconnects or the server shuts down. A sequence that can block for a long time should also watch ctx or dygo.Stopping(ctx). middleware.Compress leaves SSE streams alone.