Dockerfile

ARG  BUILDER_IMAGE=golang:1.18-alpine
############################
# STEP 1 build executable binary
############################
FROM ${BUILDER_IMAGE} as builder

# Install git + SSL ca certificates.
# Git is required for fetching the dependencies.
# Ca-certificates is required to call HTTPS endpoints.
RUN apk update && apk add --no-cache git ca-certificates tzdata gcc g++ && update-ca-certificates

WORKDIR /app

COPY go.mod go.sum ./
RUN go mod download
RUN go mod verify

COPY . .

# Build the binary
RUN CGO_ENABLED=1 GOOS=linux go build \
    -o /app/slashing-protector -a \
    -ldflags '-linkmode external -extldflags "-static -lm"' \
    ./cmd/slashing-protector

############################
# STEP 2 build a small image
############################
FROM alpine:3.15

# Import from builder.
COPY --from=builder /usr/share/zoneinfo /usr/share/zoneinfo
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
COPY --from=builder /etc/passwd /etc/passwd
COPY --from=builder /etc/group /etc/group

# Copy our static executable
COPY --from=builder /app/slashing-protector /app/slashing-protector

# Run the binary.
ENTRYPOINT ["/app/slashing-protector"]