package main

  import (
  	"context"
  	"flag"
  	"fmt"
  	"os"
  	"time"

  	"github.com/aws/aws-sdk-go/aws"
  	"github.com/aws/aws-sdk-go/aws/awserr"
  	"github.com/aws/aws-sdk-go/aws/request"
  	"github.com/aws/aws-sdk-go/aws/session"
  	"github.com/aws/aws-sdk-go/service/s3"
  )

  // Uploads a file to S3 given a bucket and object key. Also takes a duration
  // value to terminate the update if it doesn't complete within that time.
  //
  // The AWS Region needs to be provided in the AWS shared config or on the
  // environment variable as `AWS_REGION`. Credentials also must be provided
  // Will default to shared config file, but can load from environment if provided.
  //
  // Usage:
  //   # Upload myfile.txt to myBucket/myKey. Must complete within 10 minutes or will fail
  //   go run withContext.go -b mybucket -k myKey -d 10m < myfile.txt
  func main() {
  	var bucket, key string
  	var timeout time.Duration

  	flag.StringVar(&bucket, "b", "", "Bucket name.")
  	flag.StringVar(&key, "k", "", "Object key name.")
  	flag.DurationVar(&timeout, "d", 0, "Upload timeout.")
  	flag.Parse()

  	// All clients require a Session. The Session provides the client with
 	// shared configuration such as region, endpoint, and credentials. A
 	// Session should be shared where possible to take advantage of
 	// configuration and credential caching. See the session package for
 	// more information.
  	sess := session.Must(session.NewSession())

 	// Create a new instance of the service's client with a Session.
 	// Optional aws.Config values can also be provided as variadic arguments
 	// to the New function. This option allows you to provide service
 	// specific configuration.
  	svc := s3.New(sess)

  	// Create a context with a timeout that will abort the upload if it takes
  	// more than the passed in timeout.
  	ctx := context.Background()
  	var cancelFn func()
  	if timeout > 0 {
  		ctx, cancelFn = context.WithTimeout(ctx, timeout)
  	}
  	// Ensure the context is canceled to prevent leaking.
  	// See context package for more information, https://golang.org/pkg/context/
	if cancelFn != nil {
  		defer cancelFn()
	}

  	// Uploads the object to S3. The Context will interrupt the request if the
  	// timeout expires.
  	_, err := svc.PutObjectWithContext(ctx, &s3.PutObjectInput{
  		Bucket: aws.String(bucket),
  		Key:    aws.String(key),
  		Body:   os.Stdin,
  	})
  	if err != nil {
  		if aerr, ok := err.(awserr.Error); ok && aerr.Code() == request.CanceledErrorCode {
  			// If the SDK can determine the request or retry delay was canceled
  			// by a context the CanceledErrorCode error code will be returned.
  			fmt.Fprintf(os.Stderr, "upload canceled due to timeout, %v\n", err)
  		} else {
  			fmt.Fprintf(os.Stderr, "failed to upload object, %v\n", err)
  		}
  		os.Exit(1)
  	}

  	fmt.Printf("successfully uploaded file to %s/%s\n", bucket, key)
  }

  // Initial credentials loaded from SDK's default credential chain. Such as
  // the environment, shared credentials (~/.aws/credentials), or EC2 Instance
  // Role. These credentials will be used to to make the STS Assume Role API.
  sess := session.Must(session.NewSession())

  // Create the credentials from AssumeRoleProvider to assume the role
  // referenced by the "myRoleARN" ARN.
  creds := stscreds.NewCredentials(sess, "myRoleArn")

  // Create service client value configured for credentials
  // from assumed role.
  svc := s3.New(sess, &aws.Config{Credentials: creds})

  sess := session.Must(session.NewSessionWithOptions(session.Options{
      SharedConfigState: session.SharedConfigEnable,
  }))

  sess := session.Must(session.NewSession(&aws.Config{
      Region: aws.String(endpoints.UsWest2RegionID),
  }))

  svc := s3.New(sess, &aws.Config{
      Region: aws.String(endpoints.UsWest2RegionID),
  })

  ctx := context.Background()

  result, err := svc.GetObjectWithContext(ctx, &s3.GetObjectInput{
      Bucket: aws.String("my-bucket"),
      Key: aws.String("my-key"),
  })
  if err != nil {
      // Cast err to awserr.Error to handle specific error codes.
      aerr, ok := err.(awserr.Error)
      if ok && aerr.Code() == s3.ErrCodeNoSuchKey {
          // Specific error code handling
      }
      return err
  }

  // Make sure to close the body when done with it for S3 GetObject APIs or
  // will leak connections.
  defer result.Body.Close()

  fmt.Println("Object Size:", aws.Int64Value(result.ContentLength))

   objects := []string{}
   err := svc.ListObjectsPagesWithContext(ctx, &s3.ListObjectsInput{
       Bucket: aws.String(myBucket),
   }, func(p *s3.ListObjectsOutput, lastPage bool) bool {
       for _, o := range p.Contents {
           objects = append(objects, aws.StringValue(o.Key))
       }
       return true // continue paging
   })
   if err != nil {
       panic(fmt.Sprintf("failed to list objects for bucket, %s, %v", myBucket, err))
   }

   fmt.Println("Objects in bucket:", objects)

  err := svc.WaitUntilBucketExistsWithContext(ctx, &s3.HeadBucketInput{
      Bucket: aws.String(myBucket),
  })
  if err != nil {
      aerr, ok := err.(awserr.Error)
      if ok && aerr.Code() == request.WaiterResourceNotReadyErrorCode {
          fmt.Fprintf(os.Stderr, "timed out while waiting for bucket to exist")
      }
      panic(fmt.Errorf("failed to wait for bucket to exist, %v", err))
  }
  fmt.Println("Bucket", myBucket, "exists")