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< a href = "index" > Back to index< / a >
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< li > < a href = "#toc_0" > Dockerfile for Go< / a > < / li >
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< h1 id = "toc_0" > Dockerfile for Go< / h1 >
< p > Each time I start a new Go project, I repeat many steps.
Like set up < code > .gitignore< / code > , CI configs, Dockerfile, … < / p >
< p > So I decide to have a baseline Dockerfile like this:< / p >
< pre > < code class = "language-Dockerfile" > FROM golang:1.18-bullseye as builder
RUN go install golang.org/dl/go1.18@latest \
& & go1.18 download
WORKDIR /build
COPY go.mod .
COPY go.sum .
COPY vendor .
COPY . .
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GOAMD64=v3 go build -o ./app -tags timetzdata -trimpath .
FROM gcr.io/distroless/base-debian11
COPY --from=builder /build/app /app
ENTRYPOINT [" /app" ]
< / code > < / pre >
< p > I use < a href = "https://docs.docker.com/develop/develop-images/multistage-build/" > multi-stage build< / a > to keep my image size small.
First stage is < a href = "https://hub.docker.com/_/golang" > Go official image< / a > ,
second stage is < a href = "https://github.com/GoogleContainerTools/distroless" > Distroless< / a > .< / p >
< p > Before Distroless, I use < a href = "https://hub.docker.com/_/alpine" > Alpine official image< / a > ,
There is a whole discussion on the Internet to choose which is the best base image for Go.
After reading some blogs, I discover Distroless as a small and secure base image.
So I stick with it for a while.< / p >
< p > Also, remember to match Distroless Debian version with Go official image Debian version.< / p >
< pre > < code class = "language-Dockerfile" > FROM golang:1.18-bullseye as builder
< / code > < / pre >
< p > This is Go image I use as a build stage.
This can be official Go image or custom image is required in some companies.< / p >
< pre > < code class = "language-Dockerfile" > RUN go install golang.org/dl/go1.18@latest \
& & go1.18 download
< / code > < / pre >
< p > This is optional.
In my case, my company is slow to update Go image so I use this trick to install latest Go version.< / p >
< pre > < code class = "language-Dockerfile" > WORKDIR /build
COPY go.mod .
COPY go.sum .
COPY vendor .
COPY . .
< / code > < / pre >
< p > I use < code > /build< / code > to emphasize that I am building something in that directory.< / p >
< p > The 4 < code > COPY< / code > lines are familiar if you use Go enough.
First is < code > go.mod< / code > and < code > go.sum< / code > because it defines Go modules.
The second is < code > vendor< / code > , this is optional but I use it because I don’ t want each time I build Dockerfile, I need to redownload Go modules.< / p >
< pre > < code class = "language-Dockerfile" > RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GOAMD64=v3 go build -o ./app -tags timetzdata -trimpath .
< / code > < / pre >
< p > This is where I build Go program.< / p >
< p > < code > CGO_ENABLED=0< / code > because I don’ t want to mess with C libraries.
< code > GOOS=linux GOARCH=amd64< / code > is easy to explain, Linux with x86-64.
< code > GOAMD64=v3< / code > is new since < a href = "https://go.dev/doc/go1.18#amd64" > Go 1.18< / a > ,
I use v3 because I read about AMD64 version in < a href = "https://gitlab.archlinux.org/archlinux/rfcs/-/blob/master/rfcs/0002-march.rst" > Arch Linux rfcs< / a > . TLDR’ s newer computers are already x86-64-v3.< / p >
< p > < code > -tags timetzdata< / code > to embed timezone database incase base image does not have.
< code > -trimpath< / code > to support reproduce build.< / p >
< pre > < code class = "language-Dockerfile" > FROM gcr.io/distroless/base-debian11
COPY --from=builder /build/app /app
ENTRYPOINT [" /app" ]
< / code > < / pre >
< p > Finally, I copy < code > app< / code > to Distroless base image.< / p >
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