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: mockkerberos.go
    path of file: ./repos/plumber/vendor/github.com/Shopify/sarama
    
    the code of the file until where you have to start completion: package sarama

import (
	"encoding/binary"
	"encoding/hex"

	"github.com/jcmturner/gokrb5/v8/credentials"
	"github.com/jcmturner/gokrb5/v8/gssapi"
	"github.com/jcmturner/gokrb5/v8/iana/keyusage"
	"github.com/jcmturner/gokrb5/v8/messages"
	"github.com/jcmturner/gokrb5/v8/types"
)

type KafkaGSSAPIHandler struct {
	client         *MockKerberosClient
	badResponse    bool
	badKeyChecksum bool
}

func (h *KafkaGSSAPIHandler) MockKafkaGSSAPI(buffer []byte) []byte {
	// Default payload used for verify
	err := h.client.Login() // Mock client construct keys when login
	if err != nil {
		return nil
	}
	if h.badResponse { // Returns trash
		return []byte{0x00, 0x00, 0x00, 0x01, 0xAD}
	}

	pack := gssapi.WrapToken{
		Flags:     KRB5_USER_AUTH,
		EC:        12,
		RRC:       0,
		SndSeqNum: 3398292281,
		Payload:   []byte{0x11, 0x00}, // 1100
	}
	// Compute checksum
	if h.badKeyChecksum {
		pack.CheckSum = []byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}
	} else {
		err = pack.SetCheckSum(h.client.ASRep.DecryptedEncPart.Key, keyusage.GSSAPI_ACCEPTOR_SEAL)
		if err != nil {
			return nil
		}
	}

	packBytes, err := pack.Marshal()
	if err != nil {
		return nil
	}
	lenBytes := len(packBytes)
	response := make([]byte, lenBytes+4)
	copy(response[4:], packBytes)
	binary.BigEndian.PutUint32(response, uint32(lenBytes))
	return response
}

type MockKerberosClient struct {
	asRepBytes  string
	ASRep       messages.ASRep
	credentials *credentials.Credentials
	mockError   error
	errorStage  string
}

func (c *MockKerberosClient) Login() error {
	if c.errorStage == "login" && c.mockError != nil {
		return c.mockError
	}
	c.asRepBytes = "6b8202e9308202e5a003020105a10302010ba22b30293027a103020113a220041e301c301aa003020112a1131b114" +
		"558414d504c452e434f4d636c69656e74a30d1b0b4558414d504c452e434f4da4133011a003020101a10a30081b06636c69656e7" +
		"4a
    
func (c *MockKerberosClient) Login() error {
	if c.errorStage == "login" && c.mockError != nil {
		return c.mockError
	}
	c.asRepBytes = "6b8202e9308202e5a003020105a10302010ba22b30293027a103020113a220041e301c301aa003020112a1131b114" +
		"558414d504c452e434f4d636c69656e74a30d1b0b4558414d504c452e434f4da4133011a003020101a10a30081b06636c69656e7" +
		"4a5820156618201523082014ea003020105a10d1b0b4558414d504c452e434f4da220301ea003020102a11730151b066b7262746" +
		"7741b0b4558414d504c452e434f4da382011430820110a003020112a103020101a28201020481ffdb9891175d106818e61008c51" +
		"d0b3462bca92f3bf9d4cfa82de4c4d7aff9994ec87c573e3a3d54dcb2bb79618c76f2bf4a3d006f90d5bdbd049bc18f48be39203" +
		"549ca02acaf63f292b12404f9b74c34b83687119d8f56552ccc0c50ebee2a53bb114c1b4619bb1d5d31f0f49b4d40a08a9b4c046" +
		"2e1398d0b648be1c0e50c552ad16e1d8d8e74263dd0bf0ec591e4797dfd40a9a1be4ae830d03a306e053fd7586fef84ffc5e4a83" +
		"7c3122bf3e6a40fe87e84019f6283634461b955712b44a5f7386c278bff94ec2c2dc0403247e29c2450e853471ceababf9b8911f" +
		"997f2e3010b046d2c49eb438afb0f4c210821e80d4ffa4c9521eb895dcd68610b3feaa682012c30820128a003020112a282011f0" +
		"482011bce73cbce3f1dd17661c412005f0f2257c756fe8e98ff97e6ec24b7bab66e5fd3a3827aeeae4757af0c6e892948122d8b2" +
		"03c8df48df0ef5d142d0e416d688f11daa0fcd63d96bdd431d02b8e951c664eeff286a2be62383d274a04016d5f0e141da58cb86" +
		"331de64063062f4f885e8e9ce5b181ca2fdc67897c5995e0ae1ae0c171a64493ff7bd91bc6d89cd4fce1e2b3ea0a10e34b0d5eda" +
		"aa38ee727b50c5632ed1d2f2b457908e616178d0d80b72af209fb8ac9dbaa1768fa45931392b36b6d8c12400f8ded2efaa0654d0" +
		"da1db966e8b5aab4706c800f95d559664646041fdb38b411c62fc0fbe0d25083a28562b0e1c8df16e62e9d5626b0addee489835f" +
		"eedb0f26c05baa596b69b17f47920aa64b29dc77cfcc97ba47885"
	apRepBytes, err := hex.DecodeString(c.asRepBytes)
	if err != nil {
		return err
	}
	err = c.ASRep.Unmarshal(apRepBytes)
	if err != nil {
		return err
	}
	c.credentials = credentials.New("client", "EXAMPLE.COM").WithPassword("qwerty")
	_, err = c.ASRep.DecryptEncPart(c.credentials)
	if err != nil {
		return err
	}
	return nil
}