Fix body value

Signed-off-by: Мария Малыгина <m.malygina@yadro.com>

internal/s3/client.go

@@ -84,7 +84,7 @@ func (c *Client) Multipart(bucket, key string, objPartSize int, payload goja.Arr
 	result, err := uploader.Upload(context.TODO(), &s3.PutObjectInput{
 	    Bucket: aws.String(bucket),
 	    Key:    aws.String(key),
-	    Body:   payload.Bytes(),
+	    Body:   bytes.NewReader(payload.Bytes()),
     })
     if err != nil {
 		stats.Report(c.vu, objPutFails, 1)