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: presigned_put.go
    path of file: ./repos/seaweedfs/unmaintained/s3/presigned_put
    
    the code of the file until where you have to start completion: package main

import (
	"crypto/md5"
	"encoding/base64"
	"fmt"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/seaweedfs/seaweedfs/weed/util"
	"net/http"
	"strings"
	"time"
)

// Downloads an item from an S3 Bucket in the region configured in the shared config
// or AWS_REGION environment variable.
//
// Usage:
//     go run presigned_put.go
// For this exampl to work, the domainName is needd
//     weed s3 -domainName=localhost
func main() {
	h := md5.New()
	cont
    
func main() {
	h := md5.New()
	content := strings.NewReader(stringContent)
	content.WriteTo(h)

	// Initialize a session in us-west-2 that the SDK will use to load
	// credentials from the shared credentials file ~/.aws/credentials.
	sess, err := session.NewSession(&aws.Config{
		Region:   aws.String("us-east-1"),
		Endpoint: aws.String("http://localhost:8333"),
	})

	// Create S3 service client
	svc := s3.New(sess)

	putRequest, output := svc.PutObjectRequest(&s3.PutObjectInput{
		Bucket: aws.String("dev"),
		Key:    aws.String("testKey"),
	})
	fmt.Printf("output: %+v\n", output)

	md5s := base64.StdEncoding.EncodeToString(h.Sum(nil))
	putRequest.HTTPRequest.Header.Set("Content-MD5", md5s)

	url, err := putRequest.Presign(15 * time.Minute)
	if err != nil {
		fmt.Println("error presigning request", err)
		return
	}

	fmt.Println(url)

	req, err := http.NewRequest("PUT", url, strings.NewReader(stringContent))
	req.Header.Set("Content-MD5", md5s)
	if err != nil {
		fmt.Println("error creating request", url)
		return
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		fmt.Printf("error put request: %v\n", err)
		return
	}
	defer util.CloseResponse(resp)
	fmt.Printf("response: %+v\n", resp)
}