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: aws-go-sdk-lambda-example-configure-function-for-notification.go
    path of file: ./repos/aws-doc-sdk-examples/go/example_code/lambda
    
    the code of the file until where you have to start completion: // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
// snippet-start:[lambda.go.configure_function.complete]
package main

// snippet-start:[lambda.go.configure_function.imports]
import (
	"flag"
	"fmt"
	"os"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/lambda"
)

// snippet-end:[lambda.go.configure_function.imports]

func main() {
	// snippet-start:[lambda.go.configure_function.vars]
	functionPtr := flag.String("f", "", "The name of the Lambda function")
	sourcePtr := flag.String("a", "", "The ARN of the entity invoking the function")
	flag.Parse()
    
func main() {
	// snippet-start:[lambda.go.configure_function.vars]
	functionPtr := flag.String("f", "", "The name of the Lambda function")
	sourcePtr := flag.String("a", "", "The ARN of the entity invoking the function")
	flag.Parse()

	if *functionPtr == "" || *sourcePtr == "" {
		fmt.Println("You must supply the name of the function and of the entity invoking the function")
		flag.PrintDefaults()
		os.Exit(1)
	}
	// snippet-end:[lambda.go.configure_function.vars]

	// Initialize a session
	// snippet-start:[lambda.go.configure_function.session]
	sess := session.Must(session.NewSessionWithOptions(session.Options{
		SharedConfigState: session.SharedConfigEnable,
	}))

	svc := lambda.New(sess)
	// snippet-end:[lambda.go.configure_function.session]

	// snippet-start:[lambda.go.configure_function.struct]
	permArgs := &lambda.AddPermissionInput{
		Action:       aws.String("lambda:InvokeFunction"),
		FunctionName: functionPtr,
		Principal:    aws.String("s3.amazonaws.com"),
		SourceArn:    sourcePtr,
		StatementId:  aws.String("lambda_s3_notification"),
	}
	// snippet-end:[lambda.go.configure_function.struct]

	// snippet-start:[lambda.go.configure_function.add_permission]
	result, err := svc.AddPermission(permArgs)
	if err != nil {
		fmt.Println("Cannot configure function for notifications")
		os.Exit(0)
	}

	fmt.Println(result)
	// snippet-end:[lambda.go.configure_function.add_permission]
}