Dockerfile

# Multi-stage build for optimal image size
# Stage 1: Build stage
FROM golang:1.21-alpine AS builder

# Build arguments for versioning
ARG VERSION=dev
ARG GIT_COMMIT=unknown
ARG BUILD_TIME=unknown

# Install build dependencies
RUN apk add --no-cache git make

# Set working directory
WORKDIR /app

# Copy go mod files first for better layer caching
COPY go.mod go.sum ./

# Download dependencies (cached unless go.mod/go.sum change)
RUN go mod download && go mod verify

# Copy source code
COPY . .

# Build the application with version info and optimizations
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build \
    -a -installsuffix cgo \
    -ldflags="-w -s \
      -X main.Version=${VERSION} \
      -X main.GitCommit=${GIT_COMMIT} \
      -X main.BuildTime=${BUILD_TIME}" \
    -o shotify ./cmd/main.go

# Stage 2: Production stage (distroless for minimal attack surface)
FROM alpine:3.19

# Install ca-certificates for HTTPS and timezone data
RUN apk --no-cache add ca-certificates tzdata curl && \
    rm -rf /var/cache/apk/*

# Create a non-root user for security
RUN addgroup -g 1001 -S appuser && \
    adduser -u 1001 -S appuser -G appuser

WORKDIR /app

# Create uploads directory with proper permissions
RUN mkdir -p /app/uploads && chown -R appuser:appuser /app

# Copy the binary from builder stage
COPY --from=builder /app/shotify .

# Change ownership to non-root user
RUN chown appuser:appuser /app/shotify

# Switch to non-root user
USER appuser

# Expose port (configurable via PORT env)
EXPOSE 8080

# Health check
HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
  CMD curl -f http://localhost:8080/health || exit 1

# Run the application
CMD ["./shotify"]