Dockerfile

FROM --platform=$BUILDPLATFORM golang:1.19-alpine as builder

WORKDIR /app
COPY go.mod go.sum ./
RUN go mod download

COPY . .
ARG TARGETOS TARGETARCH
RUN GOOS=$TARGETOS GOARCH=$TARGETARCH go build -tags musl --ldflags "-extldflags -static"  -o gitlab ./cmd/gitlab
RUN apk add --no-cache --update curl && curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl \
    && chmod +x ./kubectl \
    && mv ./kubectl /usr/local/bin

FROM alpine

WORKDIR /

RUN apk add --no-cache --update curl git

COPY --from=builder /app/gitlab /usr/local/bin/

# musl is a libc and it look for hostname resolving in `/etc/nsswitch.conf`. glibc is a torlerance libc, it has fail-over
#   options for hostname resolving. Since alpine is a musl-based linux and `/etc/nsswitch.conf` is removed from alpine,
#   so that `--add-host` arguments does not effect. That's why we need to create image's own nsswitch.conf file.
RUN echo 'hosts: files dns' > /etc/nsswitch.conf