For Article added a consturctor func New().

pkg/article/article.go

@@ -15,6 +15,12 @@ type Article struct {
 	Body        []byte
 }
 
+func New(body, meta []byte) (article *Article, err error) {
+	article = &Article{Body: body}
+	err = article.ParseMetadata(meta)
+	return
+}
+
 func (artcl *Article) ParseMetadata(data []byte) error {
 	lines := bytes.Split(data, []byte{'\n'})
 	if len(lines) != 4 {