Don't return pointer from NewImageAttachment()

activitystreams/attachment.go

@@ -19,13 +19,13 @@ const AttachImage AttachmentType = "Image"
 // NewImageAttachment creates a new Attachment from the given URL, setting the
 // correct type and automatically detecting the MediaType based on the file
 // extension.
-func NewImageAttachment(url string) *Attachment {
+func NewImageAttachment(url string) Attachment {
 	var imgType string
 	extIdx := strings.LastIndexByte(url, '.')
 	if extIdx > -1 {
 		imgType = mime.TypeByExtension(url[extIdx:])
 	}
-	return &Attachment{
+	return Attachment{
 		Type:      AttachImage,
 		URL:       url,
 		MediaType: imgType,