build: add docker image build entrypoint

.dockerignore

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+.git
+.gitignore
+target
+tmp
+bin
+dist
+coverage
+**/.DS_Store

Dockerfile

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+FROM golang:1.24 AS builder
+
+ARG APP_VERSION="dev"
+ENV CGO_ENABLED=0 GOOS=linux GOARCH=amd64
+
+WORKDIR /src
+COPY . .
+RUN go build -trimpath -ldflags="-s -w" -o /out/chatapp3-golang ./cmd/api
+
+FROM alpine:3.20
+
+ARG APP_VERSION="dev"
+RUN apk add --no-cache ca-certificates wget
+
+WORKDIR /application
+COPY --from=builder /out/chatapp3-golang /application/service
+
+LABEL org.opencontainers.image.version="${APP_VERSION}"
+
+RUN chmod +x /application/service
+
+ENTRYPOINT ["/application/service"]

ci/build-image.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(CDPATH= cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+IMAGE_REF="${1:-}"
+APP_VERSION="${APP_VERSION:-${2:-dev}}"
+DOCKER_PLATFORM="${DOCKER_PLATFORM:-linux/amd64}"
+
+if [ -z "${IMAGE_REF}" ]; then
+  echo "usage: ci/build-image.sh <image-ref> [app-version]" >&2
+  exit 1
+fi
+
+cd "${ROOT_DIR}"
+docker build --platform "${DOCKER_PLATFORM}" --build-arg "APP_VERSION=${APP_VERSION}" -t "${IMAGE_REF}" .