How to do long polling on go?

Question

go

I want to make a long polling method in my golang api. How to do it right?
Now implemented like this:

func longPollingHandler(w http.ResponseWriter, r *http.Request) {
  done := make(chan struct{})

  go checkUpdates(done)

  select {
  case <- done:
    makeAnswer(w)
  case <- time.After(20 * time.Second):
    makeAnswer(w)
  }
}

func checkUpdates(done chan<- struct{}) {
  for i := 0; i < 20; i++ {
    
    // Тут проверяю есть ли изменения в базе
    // ...

    if db.HasChanges() {
      break;
    }

    time.Sleep(time.Second)
  }

  done <- struct{}{}
}

func makeAnswer(w http.ResponseWriter) {
  // Тут шлю ответ клиенту
  // ...
}

http.HandleFunc("/api/long_polling", longPollingHandler)

Everything works, but there was a feeling that the responses to other api methods (not long polling) began to arrive with a delay. I suspect that this is due to a slip in the goroutine.
How to do it right in the end? Please don't suggest adding 10 frameworks, libraries and dependencies.