Docker image for Go app

Use a multi-stage Dockerfile to compile your Go app in a builder stage and copy the binary to a minimal runtime stage. This reduces image size and attack surface.

# Stage 1: Build
FROM golang:1.22-alpine AS builder
WORKDIR /app
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o main .

# Stage 2: Runtime
FROM alpine:latest
RUN apk --no-cache add ca-certificates
WORKDIR /root/
COPY --from=builder /app/main .
CMD ["./main"]

This method builds your Go application inside a large container with all the necessary tools, then copies only the final executable into a tiny, empty container. It's like baking a cake in a full kitchen but serving it on a small plate to save space and keep things clean.