Finialized multipart upload and graceful shutdown. Added Dockerfile.

Dockerfile

@@ -0,0 +1,16 @@
+FROM golang:1.25-alpine AS build
+
+WORKDIR /app
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux go build -o /app/fs .
+
+FROM scratch AS runner
+
+COPY --from=build /app/fs /app/fs
+
+WORKDIR /app
+CMD ["/app/fs"]