How do I pipe the output of *discordgo.Packet to ffmpeg?

[ThallesP]

I'm trying to convert discord's opus packets to .wav using ffmpeg but I can't get it to work with discordgo. I'm a newbie to encoders so i'm probably missing something stupid. Here's my code so far:

package main

import (
	"fmt"
	"os"
	"os/exec"
	"os/signal"
	"syscall"
	"time"

	"github.com/bwmarrin/discordgo"
)

const CHANNEL_ID = "838536675240050708"
const GUILD_ID = "838505728976748624"

func main() {
	dg, err := discordgo.New("Bot " + os.Getenv("BOT_TOKEN"))

	if err != nil {
		panic(err)
	}

	err = dg.Open()

	if err != nil {
		panic(err)
	}

	dgv, err := dg.ChannelVoiceJoin(GUILD_ID, CHANNEL_ID, false, false)

	if err != nil {
		panic(err)
	}

	SaveReceivedAudio(dgv)

	fmt.Println("Bot is now running.  Press CTRL-C to exit.")
	sc := make(chan os.Signal, 1)
	signal.Notify(sc, syscall.SIGINT, syscall.SIGTERM, os.Interrupt)
	<-sc

	dg.Close()
}

func SaveReceivedAudio(v *discordgo.VoiceConnection) {
	go func(v *discordgo.VoiceConnection) {
		cmd := exec.Command("/usr/bin/ffmpeg",
			"-ac", "2",
			"-ar", "48000",
			"-f", "s16le",
			"-acodec", "libopus",
			"-i", "-", // take stdin as input
			"/home/thalles/scribe/output.opus",
		)

		cmd.Stderr = os.Stdout

		pipe, err := cmd.StdinPipe()

		if err != nil {
			panic(err)
		}

		err = cmd.Start()

		if err != nil {
			panic(err)
		}

		for {
			select {
			case packet := <-v.OpusRecv:
				/*pkrtp := &rtp.Packet{
					Header: rtp.Header{
						Version:        2,
						PayloadType:    0x78,
						SequenceNumber: packet.Sequence,
						Timestamp:      packet.Timestamp,
						SSRC:           packet.SSRC,
					},
					Payload: packet.Opus,
				}
				//pkrtp.MarshalTo(bufferRTP)
				b, _ := pkrtp.Marshal()*/

				pipe.Write(packet.Opus)
				continue
			case <-time.Tick(10 * time.Second):
				pipe.Close()
				fmt.Println("stopping", cmd.Process.Signal(os.Interrupt))
				return
			}

		}
	}(v)
}

I've seen the use of oggwriter but I'm scared that it'll cause overhead