update Dockerfile

Dockerfile

@@ -1,13 +1,21 @@
-FROM costbase:2.0
+FROM costbase:2.0 as build
 
 RUN mv /home/ConstructionCost /home/YangHuCost
 
 WORKDIR /home/YangHuCost
 
-COPY . /home/YangHuCost
+COPY package.json /home/YangHuCost
 
 RUN cnpm install
 
+FROM base-alpine:latest
+
+COPY --from=build /home/YangHuCost /home/YangHuCost
+
+COPY . /home/YangHuCost
+
+WORKDIR /home/YangHuCost
+
 RUN gulp build
 
 ENV NODE_ENV=prod