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: alb.go
    path of file: ./repos/tegola/vendor/github.com/akrylysov/algnhsa
    
    the code of the file until where you have to start completion: package algnhsa

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"net/url"
	"strings"

	"github.com/aws/aws-lambda-go/events"
)

/*
AWS Documentation:

- https://docs.aws.amazon.com/lambda/latest/dg/services-alb.html
*/

var (
	errALBUnexpectedRequest         = errors.New("expected ALBTargetGroupRequest event")
	errALBExpectedMultiValueHeaders = errors.New("expected multi value headers; enable Multi value headers in target group settings")
)

func getALBSourceIP(event events.ALBTargetGroupRequest) string 
    
func newALBRequest(ctx context.Context, payload []byte, opts *Options) (lambdaRequest, error) {
	var event events.ALBTargetGroupRequest
	if err := json.Unmarshal(payload, &event); err != nil {
		return lambdaRequest{}, err
	}
	if event.RequestContext.ELB.TargetGroupArn == "" {
		return lambdaRequest{}, errALBUnexpectedRequest
	}
	if len(event.MultiValueHeaders) == 0 {
		return lambdaRequest{}, errALBExpectedMultiValueHeaders
	}

	for _, vals := range event.MultiValueQueryStringParameters {
		for i, v := range vals {
			unescaped, err := url.QueryUnescape(v)
			if err != nil {
				return lambdaRequest{}, err
			}
			vals[i] = unescaped
		}
	}

	req := lambdaRequest{
		HTTPMethod:                      event.HTTPMethod,
		Path:                            event.Path,
		MultiValueQueryStringParameters: event.MultiValueQueryStringParameters,
		MultiValueHeaders:               event.MultiValueHeaders,
		Body:                            event.Body,
		IsBase64Encoded:                 event.IsBase64Encoded,
		SourceIP:                        getALBSourceIP(event),
		Context:                         context.WithValue(ctx, RequestTypeALB, event),
		requestType:                     RequestTypeALB,
	}

	return req, nil
}