Pion WebRTC implementing NACK response

example.go

// Define codec and create local track
videoRTCPFeedback := []webrtc.RTCPFeedback{{"goog-remb", ""}, {"ccm", "fir"}, {"nack", ""}, {"nack", "pli"}}
codec := webrtc.RTPCodecParameters{
    RTPCodecCapability: webrtc.RTPCodecCapability{webrtc.MimeTypeH264, 90000, 0, "level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f", videoRTCPFeedback},
    PayloadType:        102,
}
vidTrack, err := webrtc.NewTrackLocalStaticRTP(codec.RTPCodecCapability, "video", "vid")
if err != nil {
    panic(err)
}

// Register codecs into media engine
mediaEngine := &webrtc.MediaEngine{}
if err := mediaEngine.RegisterCodec(codec, webrtc.RTPCodecTypeVideo); err != nil {
    panic(err)
}

// Enable NACK interceptor
intRegistry := &interceptor.Registry{}
if err := webrtc.ConfigureNack(mediaEngine, intRegistry); err != nil {
    panic(err)
}

// Create API to extract PeerConnection later
api := webrtc.NewAPI(webrtc.WithMediaEngine(mediaEngine), webrtc.WithInterceptorRegistry(intRegistry))

// Prepare the configuration
configuration := webrtc.Configuration{
    ICEServers: []webrtc.ICEServer{
        {
            URLs: []string{"stun:stun.l.google.com:19302"},
        },
    },
}

// Create peer connection
serverConnection, err := api.NewPeerConnection(configuration)
if err != nil {
    panic(err)
}

// Add video track to connection
rtcpSender, err := serverConnection.AddTrack(vidTrack)
if err != nil {
    panic(err)
}

// Create UDP listener to read from ffmpeg
vidListener, err := net.ListenUDP("udp", &net.UDPAddr{IP: net.ParseIP(receiveIP), Port: 5004})
if err != nil {
    panic(err)
}

// Start video track reader
go func() {
    inboundRTPPacket := make([]byte, rtcBufferSize)
    fmt.Println("Started reading from video port")
    for {
        n, _, err := vidListener.ReadFrom(inboundRTPPacket)
        if err != nil {
            break
        }
        // write to track
        if _, err = vidTrack.Write(inboundRTPPacket[:n]); err != nil {
            if errors.Is(err, io.ErrClosedPipe) {
                break
            }
            panic(err)
        }
    }
    fmt.Println("Stopped reading from video port")
}()

// Read rtcp info like NACK from client
go func() {
    for {
        rtcpList, _, err := rtcpSender.ReadRTCP()
        if err != nil {
            panic(err)
        }
        fmt.Println(rtcpList)
    }
}()
// ... (receive sdp from browser client and initiate webrtc connection)