func (l CustomLayer) LayerPayload() []byte {
	return l.restOfData
}
LayerPayload returns the subsequent layer built
on top of our layer or raw payload
package main
import (
	"fmt"
	"github.com/google/gopacket"
)
type CustomLayer struct {
	SomeByte    byte
	AnotherByte byte
	restOfData  []byte
}
var CustomLayerType = gopacket.RegisterLayerType(
	2001,
	gopacket.LayerTypeMetadata{
		"CustomLayerType",
		gopacket.DecodeFunc(decodeCustomLayer),
	},
)
func (l CustomLayer) LayerType() gopacket.LayerType {
	return CustomLayerType
}
func (l CustomLayer) LayerContents() []byte {
	return []byte{l.SomeByte, l.AnotherByte}
}