fix bug where subsequent reads of the same article come back empty

main.go

@@ -122,7 +122,7 @@ func (b *backend) GetArticles(_ *nntp.Group, from, to int64) ([]nntpserver.Numbe
 		if num >= from && num <= to {
 			numbered = append(numbered, nntpserver.NumberedArticle{
 				Num:     num,
-				Article: msg,
+				Article: copyArticle(msg),
 			})
 		}
 	}
@@ -145,7 +145,7 @@ func (b *backend) GetArticle(_ *nntp.Group, messageID string) (*nntp.Article, er
 
 	num, err := strconv.Atoi(messageID)
 	if err == nil && num <= len(b.messages) {
-		return b.messages[num-1], nil
+		return copyArticle(b.messages[num-1]), nil
 	}
 
 	return nil, nntpserver.ErrInvalidMessageID
@@ -171,6 +171,13 @@ func (b backend) Post(article *nntp.Article) error {
 	return appendMessage(msg)
 }
 
+func copyArticle(article *nntp.Article) *nntp.Article {
+	var out nntp.Article
+	out = *article
+	out.Body = bytes.NewBuffer(article.Body.(*bytes.Buffer).Bytes())
+	return &out
+}
+
 type irisMsg struct {
 	Hash      string  `json:"hash"`
 	EditHash  *string `json:"edit_hash"`