Http4s: Stream a constant String until the response is ready (might be useful for preventing connection to be closed)

Http4sStreamStringUntilResponseIsReady.scala

  def constantStringThenContent[F[_] : Timer : Concurrent, A](constantString: String, result: F[A])(
    implicit W: EntityEncoder[F, A]
  ): Response[F] = {
    val resultStream = Stream.eval(result)
    val preStream = EntityEncoder.stringEncoder[F].toEntity(constantString).body
    val composedStream = (Stream[F, Option[A]](None, None, None) ++ resultStream.map(Option.apply))
      .switchMap[F, Byte] {
        case None =>
          fs2.Stream.awakeEvery[F](10.second).flatMap(_ => preStream)
        case Some(v) => W.toEntity(v).body
      }

    val headers =
      W.headers.get(`Transfer-Encoding`) match {
        case Some(transferCoding) if transferCoding.hasChunked =>
          W.headers
        case _ =>
          W.headers.put(`Transfer-Encoding`(TransferCoding.chunked))
      }
    Response(status = Status.Ok, headers = headers, body = composedStream)
  }