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: client_auth.go
    path of file: ./repos/sliver/vendor/golang.org/x/crypto/ssh
    
    the code of the file until where you have to start completion: // Copyright 2011 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 ssh

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"strings"
)

type authResult int

const (
	authFailure authResult = iota
	authPartialSuccess
	authSuccess
)

// clientAuthenticate authenticates with the remote server. See RFC 4252.
func (c *connection) clientAuthenticate(config *ClientConfig) error {
	// initiate user auth session
	if err := c.transport.writePacket(Marshal(&serviceRequestMsg{serviceUserAuth})); err != nil {
		return err
	}
	packet, err := c.transport.readPacket()
	if err != nil {
		return err
	}
	// The server may choose to send a SSH_MSG_EXT_INFO at this point (if we
	// advertised willingness to receive one, which we always do) or not. See
	// RFC 8308, Section 2.4.
	extensions := make(map[string][]byte)
	if len(packet) > 0 && packet[0] == msgExtInfo {
		var extInfo extInfoMsg
		if err := Unmarshal(packet, &extInfo); err != nil {
			return err
		}
		payload := extInfo.Payload
		for i := uint32(0); i < extInfo.NumExtensions; i++ {
			name, rest, ok := parseString(payload)
			if !ok {
				return parseError(msgExtInfo)
			}
			value, rest, ok := parseString(rest)
			if !ok {
				return parseError(msgExtInfo)
			}
			extensions[string(name)] = value
			payload = rest
		}
		packet, err = c.transport.readPacket()
		if err != nil {
			return err
		}
	}
	var serviceAccept serviceAcceptMsg
	if err := Unmarshal(packet, &serviceAccept); err != nil {
		return err
	}

	// during the authentication phase the client first attempts the "none" method
	// then any untried m
    
func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packetConn, rand io.Reader, _ map[string][]byte) (authResult, []string, error) {
	type initiateMsg struct {
		User       string `sshtype:"50"`
		Service    string
		Method     string
		Language   string
		Submethods string
	}

	if err := c.writePacket(Marshal(&initiateMsg{
		User:    user,
		Service: serviceSSH,
		Method:  "keyboard-interactive",
	})); err != nil {
		return authFailure, nil, err
	}

	gotMsgExtInfo := false
	for {
		packet, err := c.readPacket()
		if err != nil {
			return authFailure, nil, err
		}

		// like handleAuthResponse, but with less options.
		switch packet[0] {
		case msgUserAuthBanner:
			if err := handleBannerResponse(c, packet); err != nil {
				return authFailure, nil, err
			}
			continue
		case msgExtInfo:
			// Ignore post-authentication RFC 8308 extensions, once.
			if gotMsgExtInfo {
				return authFailure, nil, unexpectedMessageError(msgUserAuthInfoRequest, packet[0])
			}
			gotMsgExtInfo = true
			continue
		case msgUserAuthInfoRequest:
			// OK
		case msgUserAuthFailure:
			var msg userAuthFailureMsg
			if err := Unmarshal(packet, &msg); err != nil {
				return authFailure, nil, err
			}
			if msg.PartialSuccess {
				return authPartialSuccess, msg.Methods, nil
			}
			return authFailure, msg.Methods, nil
		case msgUserAuthSuccess:
			return authSuccess, nil, nil
		default:
			return authFailure, nil, unexpectedMessageError(msgUserAuthInfoRequest, packet[0])
		}

		var msg userAuthInfoRequestMsg
		if err := Unmarshal(packet, &msg); err != nil {
			return authFailure, nil, err
		}

		// Manually unpack the prompt/echo pairs.
		rest := msg.Prompts
		var prompts []string
		var echos []bool
		for i := 0; i < int(msg.NumPrompts); i++ {
			prompt, r, ok := parseString(rest)
			if !ok || len(r) == 0 {
				return authFailure, nil, errors.New("ssh: prompt format error")
			}
			prompts = append(prompts, string(prompt))
			echos = append(echos, r[0] != 0)
			rest = r[1:]
		}

		if len(rest) != 0 {
			return authFailure, nil, errors.New("ssh: extra data following keyboard-interactive pairs")
		}

		answers, err := cb(msg.Name, msg.Instruction, prompts, echos)
		if err != nil {
			return authFailure, nil, err
		}

		if len(answers) != len(prompts) {
			return authFailure, nil, fmt.Errorf("ssh: incorrect number of answers from keyboard-interactive callback %d (expected %d)", len(answers), len(prompts))
		}
		responseLength := 1 + 4
		for _, a := range answers {
			responseLength += stringLength(len(a))
		}
		serialized := make([]byte, responseLength)
		p := serialized
		p[0] = msgUserAuthInfoResponse
		p = p[1:]
		p = marshalUint32(p, uint32(len(answers)))
		for _, a := range answers {
			p = marshalString(p, []byte(a))
		}

		if err := c.writePacket(serialized); err != nil {
			return authFailure, nil, err
		}
	}
}