code: public static int initiateStream(ChannelHandlerContext ctx, Http2Connection connection,
                                       Http2ClientChannel http2ClientChannel,
                                       OutboundMsgHolder outboundMsgHolder) throws Http2Exception {
          int streamId = getNextStreamId(connection);
          createStream(connection, streamId);
          http2ClientChannel.putInFlightMessage(streamId, outboundMsgHolder);
          http2ClientChannel.getDataEventListeners()
                  .forEach(dataEventListener -> dataEventListener.onStreamInit(ctx, streamId));
          return streamId;
      }
docs: Initiates a HTTP2 stream.
  
  @param ctx                the channel handler context
  @param connection         the HTTP2 connection
  @param http2ClientChannel the client channel related to the handler
  @param outboundMsgHolder  the outbound message holder
  @return stream id of next stream
  @throws Http2Exception if a protocol-related error occurred