remove debug

logb.go

@@ -85,6 +85,9 @@ func logf(lvl Level, form string, args ...interface{}) {
 		return
 	}
 	form = fmt.Sprintf("[%v] %s\n", lvl.String()[:3], form)
-	fmt.Fprintf(os.Stderr, "stderr: "+form, args...)
+	if writer != os.Stderr {
 		fmt.Fprintf(writer, form, args...)
+	} else {
+		fmt.Fprintf(os.Stderr, form, args...)
+	}
 }