feed.go: close twtxt file after creating it

feed.go

@@ -41,7 +41,11 @@ func prependToFile(filename, data string) error {
 func Post(twt, feedFile string, ascend bool) error {
 	fileInfo, err := os.Stat(feedFile)
 	if err != nil {
-		os.Create(feedFile)
+		f, err := os.Create(feedFile)
+		if err != nil {
+			return err
+		}
+		f.Close()
 	} else if fileInfo.IsDir() {
 		return errors.New("Feed file is a directory")
 	}