2022-12-25 19:13:58 +00:00
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2023-01-21 19:29:57 +00:00
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2022-07-10 11:09:42 +00:00
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2022-12-25 19:13:58 +00:00
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2022-12-30 10:08:50 +00:00
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<div><a href="index">Index</a></div>
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2022-12-30 09:26:06 +00:00
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<h1>
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<a
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id="user-content-dockerfile-for-go"
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class="anchor"
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aria-hidden="true"
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href="#dockerfile-for-go"
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><span aria-hidden="true" class="octicon octicon-link"></span></a
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>Dockerfile for Go
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</h1>
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<p>
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Each time I start a new Go project, I repeat many steps. Like set up
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<code>.gitignore</code>, CI configs, Dockerfile, ...
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</p>
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<p>So I decide to have a baseline Dockerfile like this:</p>
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<div class="highlight highlight-source-dockerfile">
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<pre><span class="pl-k">FROM</span> golang:1.19-bullseye as builder
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<span class="pl-k">RUN</span> go install golang.org/dl/go1.19@latest \
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2022-10-09 10:45:31 +00:00
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&& go1.19 download
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<span class="pl-k">WORKDIR</span> /build
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<span class="pl-k">COPY</span> go.mod .
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<span class="pl-k">COPY</span> go.sum .
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<span class="pl-k">COPY</span> vendor .
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<span class="pl-k">COPY</span> . .
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<span class="pl-k">RUN</span> CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GOAMD64=v3 go build -o ./app -tags timetzdata -trimpath .
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2022-12-25 19:13:58 +00:00
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<span class="pl-k">FROM</span> gcr.io/distroless/base-debian11
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<span class="pl-k">COPY</span> --from=builder /build/app /app
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2022-12-30 09:26:06 +00:00
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<span class="pl-k">ENTRYPOINT</span> [<span class="pl-s">"/app"</span>]</pre>
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</div>
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<p>
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I use
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<a
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href="https://docs.docker.com/develop/develop-images/multistage-build/"
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rel="nofollow"
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>multi-stage build</a
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>
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to keep my image size small. First stage is
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<a href="https://hub.docker.com/_/golang" rel="nofollow"
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>Go official image</a
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>, second stage is
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<a href="https://github.com/GoogleContainerTools/distroless">Distroless</a
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>.
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</p>
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<p>
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Before Distroless, I use
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<a href="https://hub.docker.com/_/alpine" rel="nofollow"
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>Alpine official image</a
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>, There is a whole discussion on the Internet to choose which is the best
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base image for Go. After reading some blogs, I discover Distroless as a
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small and secure base image. So I stick with it for a while.
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</p>
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<p>
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Also, remember to match Distroless Debian version with Go official image
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Debian version.
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</p>
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<div class="highlight highlight-source-dockerfile">
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<pre><span class="pl-k">FROM</span> golang:1.19-bullseye as builder</pre>
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</div>
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<p>
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This is Go image I use as a build stage. This can be official Go image or
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custom image is required in some companies.
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</p>
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<div class="highlight highlight-source-dockerfile">
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<pre><span class="pl-k">RUN</span> go install golang.org/dl/go1.19@latest \
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&& go1.19 download</pre>
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</div>
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<p>
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This is optional. In my case, my company is slow to update Go image so I
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use this trick to install latest Go version.
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</p>
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<div class="highlight highlight-source-dockerfile">
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<pre><span class="pl-k">WORKDIR</span> /build
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<span class="pl-k">COPY</span> go.mod .
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<span class="pl-k">COPY</span> go.sum .
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<span class="pl-k">COPY</span> vendor .
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2022-12-30 09:26:06 +00:00
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<span class="pl-k">COPY</span> . .</pre>
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</div>
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<p>
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I use <code>/build</code> to emphasize that I am building something in
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that directory.
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</p>
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<p>
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The 4 <code>COPY</code> lines are familiar if you use Go enough. First is
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<code>go.mod</code> and <code>go.sum</code> because it defines Go modules.
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The second is <code>vendor</code>, this is optional but I use it because I
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don't want each time I build Dockerfile, I need to redownload Go modules.
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</p>
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<div class="highlight highlight-source-dockerfile">
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<pre><span class="pl-k">RUN</span> CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GOAMD64=v3 go build -o ./app -tags timetzdata -trimpath .</pre>
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</div>
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<p>This is where I build Go program.</p>
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<p>
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<code>CGO_ENABLED=0</code> because I don't want to mess with C libraries.
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<code>GOOS=linux GOARCH=amd64</code> is easy to explain, Linux with
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x86-64. <code>GOAMD64=v3</code> is new since
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<a href="https://go.dev/doc/go1.18#amd64" rel="nofollow">Go 1.18</a>, I
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use v3 because I read about AMD64 version in
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<a
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href="https://gitlab.archlinux.org/archlinux/rfcs/-/blob/master/rfcs/0002-march.rst"
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rel="nofollow"
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>Arch Linux rfcs</a
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>. TLDR's newer computers are already x86-64-v3.
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</p>
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<p>
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<code>-tags timetzdata</code> to embed timezone database incase base image
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does not have. <code>-trimpath</code> to support reproduce build.
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</p>
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<div class="highlight highlight-source-dockerfile">
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<pre><span class="pl-k">FROM</span> gcr.io/distroless/base-debian11
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2022-12-25 19:13:58 +00:00
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<span class="pl-k">COPY</span> --from=builder /build/app /app
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2022-07-10 11:09:42 +00:00
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2022-12-30 09:26:06 +00:00
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<span class="pl-k">ENTRYPOINT</span> [<span class="pl-s">"/app"</span>]</pre>
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</div>
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<p>Finally, I copy <code>app</code> to Distroless base image.</p>
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2022-07-10 11:09:42 +00:00
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2022-12-25 19:22:39 +00:00
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<div>
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Feel free to ask me via
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<a href="mailto:hauvipapro+posts@gmail.com">email</a> or
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2022-12-30 09:55:38 +00:00
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<a rel="me" href="https://hachyderm.io/@haunguyen">Mastodon</a>. Source
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code is available on
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<a href="https://github.com/haunt98/posts-go">GitHub</a>
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2022-12-25 19:22:39 +00:00
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2022-12-25 19:13:58 +00:00
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