This content originally appeared on DEV Community and was authored by Young Yoshie
Each time I start a new Go project, I repeat many steps.
Like set up .gitignore, CI configs, Dockerfile, ...
So I decide to have a baseline Dockerfile like this:
FROM golang:1.18beta1-bullseye as builder
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 main.go
FROM gcr.io/distroless/base-debian11
COPY --from=builder /build/app /app
ENTRYPOINT ["/app"]
I use multi-stage build to keep my image size small.
First stage is Go official image,
second stage is Distroless.
Before Distroless, I use Alpine official image,
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.
Also, remember to match Distroless Debian version with Go official image Debian version.
FROM golang:1.18beta1-bullseye as builder
This is Go image I use as a build stage.
WORKDIR /build
COPY go.mod .
COPY go.sum .
COPY vendor .
COPY . .
I use /build to emphasize that I am building something in that directory.
The 4 COPY lines are familiar if you use Go enough.
First is go.mod and go.sum because it defines Go modules.
The second is vendor because I use it a lot, this is not necessary but I use it because I don't want each time I build Dockerfile, I need to redownload Go modules.
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GOAMD64=v3 go build -o ./app main.go
This is where I build Go program.
CGO_ENABLED=0 because I don't want to mess with C libraries.
GOOS=linux GOARCH=amd64 is easy to explain, Linux with x86-64.
GOAMD64=v3 is new since Go 1.18,
I use v3 because I read about AMD64 version in Arch Linux rfcs. TLDR's newer computers are already x86-64-v3.
FROM gcr.io/distroless/base-debian11
COPY --from=builder /build/app /app
ENTRYPOINT ["/app"]
Finally, I copy app to Distroless base image.
This content originally appeared on DEV Community and was authored by Young Yoshie
Young Yoshie | Sciencx (2021-12-19T04:46:17+00:00) Dockerfile for Go. Retrieved from https://www.scien.cx/2021/12/19/dockerfile-for-go/
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