diff --git a/Dockerfile b/Dockerfile
index c4b46c0..68c799a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ubuntu:16.04 AS builder
+FROM ubuntu:latest AS builder
 
 ENV APP_NAME ngtd
 
@@ -47,7 +47,6 @@ RUN CGO_ENABLED=1 \
 FROM scratch
 LABEL maintainer "kpango <i.can.feel.gravity@gmail.com>, Kosuke Morimoto <kou.morimoto@gmail.com>"
 
-ENV APP_USER ngtd-user
 ENV APP_NAME ngtd
 
 # Copy certificates for SSL/TLS
diff --git a/README.md b/README.md
index 42875d4..6b33de0 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# NGTD: Serving [NGT](https://github.com/yahoojapan/NGT) over HTTP or gRPC. [![License: Apache](https://img.shields.io/badge/License-Apache%202.0-blue.svg?style=flat-square)](https://opensource.org/licenses/Apache-2.0) [![release](https://img.shields.io/github/release/yahoojapan/ngtd.svg?style=flat-square)](https://github.com/yahoojapan/ngtd/releases/latest) [![CircleCI](https://circleci.com/gh/yahoojapan/ngtd.svg)](https://circleci.com/gh/yahoojapan/ngtd) [![codecov](https://codecov.io/gh/yahoojapan/ngtd/branch/master/graph/badge.svg)](https://codecov.io/gh/yahoojapan/ngtd) [![Go Report Card](https://goreportcard.com/badge/github.com/yahoojapan/ngtd)](https://goreportcard.com/report/github.com/yahoojapan/ngtd) [![GolangCI](https://golangci.com/badges/github.com/yahoojapan/ngtd.svg?style=flat-square)](https://golangci.com/r/github.com/yahoojapan/ngtd) [![Codacy Badge](https://api.codacy.com/project/badge/Grade/b03d543ee4a9448ba6d25f94f4989ba4)](https://www.codacy.com/app/i.can.feel.gravity/ngtd?utm_source=github.com&amp;utm_medium=referral&amp;utm_content=yahoojapan/ngtd&amp;utm_campaign=Badge_Grade) [![GoDoc](http://godoc.org/github.com/yahoojapan/ngtd?status.svg)](http://godoc.org/github.com/yahoojapan/ngtd)
+# NGTD: Serving [NGT](https://github.com/yahoojapan/NGT) over HTTP or gRPC. [![License: Apache](https://img.shields.io/badge/License-Apache%202.0-blue.svg?style=flat-square)](https://opensource.org/licenses/Apache-2.0) [![release](https://img.shields.io/github/release/yahoojapan/ngtd.svg?style=flat-square)](https://github.com/yahoojapan/ngtd/releases/latest) [![CircleCI](https://circleci.com/gh/yahoojapan/ngtd.svg)](https://circleci.com/gh/yahoojapan/ngtd) [![codecov](https://codecov.io/gh/yahoojapan/ngtd/branch/master/graph/badge.svg)](https://codecov.io/gh/yahoojapan/ngtd) [![Go Report Card](https://goreportcard.com/badge/github.com/yahoojapan/ngtd)](https://goreportcard.com/report/github.com/yahoojapan/ngtd) [![Codacy Badge](https://api.codacy.com/project/badge/Grade/b03d543ee4a9448ba6d25f94f4989ba4)](https://www.codacy.com/app/i.can.feel.gravity/ngtd?utm_source=github.com&amp;utm_medium=referral&amp;utm_content=yahoojapan/ngtd&amp;utm_campaign=Badge_Grade) [![GoDoc](http://godoc.org/github.com/yahoojapan/ngtd?status.svg)](http://godoc.org/github.com/yahoojapan/ngtd)
 
 Description
 -----------