You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: buffer.go
    path of file: ./repos/goreportcard/vendor/github.com/golang/protobuf/proto
    
    the code of the file until where you have to start completion: // Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package proto

import (
	"errors"
	"fmt"

	"google.golang.org/protobuf/en
    
func consumeGroup(b []byte) ([]byte, int, error) {
	b0 := b
	depth := 1 // assume this follows a start group marker
	for {
		_, wtyp, tagLen := protowire.ConsumeTag(b)
		if tagLen < 0 {
			return nil, 0, protowire.ParseError(tagLen)
		}
		b = b[tagLen:]

		var valLen int
		switch wtyp {
		case protowire.VarintType:
			_, valLen = protowire.ConsumeVarint(b)
		case protowire.Fixed32Type:
			_, valLen = protowire.ConsumeFixed32(b)
		case protowire.Fixed64Type:
			_, valLen = protowire.ConsumeFixed64(b)
		case protowire.BytesType:
			_, valLen = protowire.ConsumeBytes(b)
		case protowire.StartGroupType:
			depth++
		case protowire.EndGroupType:
			depth--
		default:
			return nil, 0, errors.New("proto: cannot parse reserved wire type")
		}
		if valLen < 0 {
			return nil, 0, protowire.ParseError(valLen)
		}
		b = b[valLen:]

		if depth == 0 {
			return b0[:len(b0)-len(b)-tagLen], len(b0) - len(b), nil
		}
	}
}