upload/aws: delete the s3 object after the snapshot is imported

After the snapshot is imported to EC2, there's no point in having the s3
object anymore. If the s3 object is not deleted, the user will be charged
for it periodically, while the object doesn't provide any value.

internal/upload/awsupload/awsupload.go

@@ -9,12 +9,14 @@ import (
 	"github.com/aws/aws-sdk-go/aws/request"
 	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/aws/aws-sdk-go/service/ec2"
+	"github.com/aws/aws-sdk-go/service/s3"
 	"github.com/aws/aws-sdk-go/service/s3/s3manager"
 )
 
 type AWS struct {
 	uploader *s3manager.Uploader
 	importer *ec2.EC2
+	s3       *s3.S3
 }
 
 func New(region, accessKeyID, accessKey string) (*AWS, error) {
@@ -33,6 +35,7 @@ func New(region, accessKeyID, accessKey string) (*AWS, error) {
 	return &AWS{
 		uploader: s3manager.NewUploader(sess),
 		importer: ec2.New(sess),
+		s3:       s3.New(sess),
 	}, nil
 }
 
@@ -125,6 +128,15 @@ func (a *AWS) Register(name, bucket, key string) (*string, error) {
 		return nil, err
 	}
 
+	// we no longer need the object in s3, let's just delete it
+	_, err = a.s3.DeleteObject(&s3.DeleteObjectInput{
+		Bucket: aws.String(bucket),
+		Key:    aws.String(key),
+	})
+	if err != nil {
+		return nil, err
+	}
+
 	importOutput, err := a.importer.DescribeImportSnapshotTasks(
 		&ec2.DescribeImportSnapshotTasksInput{
 			ImportTaskIds: []*string{