Adding Dockerfile.

Dockerfile

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+FROM golang:1.13-alpine AS build
+
+WORKDIR /migrator
+
+RUN apk add --no-cache build-base curl git
+
+ADD ./old /migrator/old
+ADD ./go.mod /migrator/go.mod
+ADD ./magnetico-migrator.go /migrator/magnetico-migrator.go
+
+RUN go build "-ldflags=-s -w" -o /migrator/migrator .
+
+FROM alpine:latest
+LABEL maintainer="skobkin-ru@ya.ru"
+
+WORKDIR /
+
+VOLUME /data
+
+COPY --from=build /migrator/migrator /migrator
+
+ENTRYPOINT ["/migrator"]