添加dockerfile的支持

Dockerfile

+FROM golang:1.16.3-alpine3.13 as build
+
+RUN set -ex \
+&& go env -w GO111MODULE=on \
+&& go env -w GOPROXY=https://goproxy.cn,direct
+
+ENV CGO_ENABLED=0
+
+WORKDIR /app
+
+COPY . /app
+
+RUN go build -o logtransfer ./
+
+FROM alpine as production
+
+WORKDIR /app
+
+COPY --from=build /app /app
+
+ENTRYPOINT ["/app/logtransfer"]