message format issue about kafka-go HOT 6 CLOSED

package main

import (
	"bytes"
	"context"
	"encoding/binary"
	"fmt"

	"github.com/golang/snappy"
	kafka "github.com/kafka-go"
)

var xerialHeader = []byte{130, 83, 78, 65, 80, 80, 89, 0}

// Decode decodes snappy data whether it is traditional unframed
// or includes the xerial framing format.
func Decode(src []byte) ([]byte, error) {
	if !bytes.Equal(src[:8], xerialHeader) {
		return snappy.Decode(nil, src)
	}

	var (
		pos   = uint32(16)
		max   = uint32(len(src))
		dst   = make([]byte, 0, len(src))
		chunk []byte
		err   error
	)
	for pos < max {
		size := binary.BigEndian.Uint32(src[pos : pos+4])
		pos += 4

		chunk, err = snappy.Decode(chunk, src[pos:pos+size])
		if err != nil {
			return nil, err
		}
		pos += size
		dst = append(dst, chunk...)
	}
	return dst, nil
}

func main() {
	r := kafka.NewReader(kafka.ReaderConfig{
		Brokers:   []string{"kafka-1:9092"},
		Topic:     "server-invalid",
		Partition: 0,
		MinBytes:  10e3, // 10KB
		MaxBytes:  10e6, // 10MB
	})
	r.SetOffset(46356099)

	for {
		m, err := r.ReadMessage(context.Background())
		if err != nil {
			fmt.Println(err)
			break
		}
		data, err := Decode(m.Value)
		if err != nil {
			fmt.Println(err)
			break
		}
		for i, c := range data {
			fmt.Printf("%x ", c)
		}
		fmt.Printf("\n")
		fmt.Printf("message at offset %d: %s = %s\n", m.Offset, string(m.Key), string(data))
		break
	}

	r.Close()
}

joe@WASP-12b ~/src/github.com/segmentio/kafka-go $ git rev-parse --verify HEAD                                                                                                                       
48c37f796910d8154479aaa04ade5843ae4f55d0

joe@WASP-12b ~/src/github.com/segmentio/kafka-go $ git rev-parse --verify origin/master                                                                                                              
48c37f796910d8154479aaa04ade5843ae4f55d0

joe@WASP-12b ~/src/github.com/customerio/x/kafka-test $ ./kafka-test > "output.log"

0 0 0 0 33 9c 1a 93 0 2 a8 3f 27 cf 51 a7 0 0 ff ff ff ff 0 2 a8 31
...
message at offset 865868659:  = 3���?'�Q������1{"level":"info",