Dockerfile

# Build the manager binary.
# Run the build stage natively on the build host (BUILDPLATFORM) and
# cross-compile to the target platform via GOOS/GOARCH. The build is
# CGO_ENABLED=0, so this avoids running the Go toolchain under QEMU emulation
# for a non-native target arch (e.g. arm64 on an amd64 runner) — much faster.
ARG GOLANG_IMAGE=golang:1.25
FROM --platform=${BUILDPLATFORM} ${GOLANG_IMAGE} AS builder
ARG TARGETOS
ARG TARGETARCH

WORKDIR /workspace
# Download dependencies as a separate, cacheable layer so they are only
# re-fetched when go.mod/go.sum change.
COPY go.mod go.mod
COPY go.sum go.sum
RUN go mod download

# Copy the Go source (relies on .dockerignore to filter).
COPY . .

# Build
# the GOARCH has no default value to allow the binary to be built according to the host where the command
# was called. For example, if we call make docker-build in a local env which has the Apple Silicon M1 SO
# the docker BUILDPLATFORM arg will be linux/arm64 when for Apple x86 it will be linux/amd64. Therefore,
# by leaving it empty we can ensure that the container and binary shipped on it will have the same platform.
RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o manager cmd/main.go

# Use distroless as minimal base image to package the manager binary
# Refer to https://github.com/GoogleContainerTools/distroless for more details
FROM gcr.io/distroless/static:nonroot
WORKDIR /
COPY --from=builder /workspace/manager .
USER 65532:65532

ENTRYPOINT ["/manager"]