Dockerfile

# Build args:
#   TARGETOS, TARGETARCH - target platform for cross-compilation, set by buildx
ARG TARGETOS
ARG TARGETARCH

FROM --platform=$BUILDPLATFORM golang:1.26 AS builder
ARG TARGETOS
ARG TARGETARCH

WORKDIR /workspace
COPY go.mod go.mod
COPY go.sum go.sum
# Cache deps in their own layer before copying source.
RUN go mod download

COPY cmd/main.go cmd/main.go
COPY api/ api/
COPY internal/ internal/

# GOARCH left unset (unlike GOOS) so the binary matches BUILDPLATFORM's
# host arch unless TARGETARCH is explicitly overridden.
RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o manager cmd/main.go

# distroless/static: minimal, no shell or package manager.
FROM gcr.io/distroless/static:nonroot
WORKDIR /
COPY --from=builder /workspace/manager .
USER 65532:65532

ENTRYPOINT ["/manager"]