Use multi-stage builds

Dockerfile

@@ -1,7 +1,13 @@
-FROM golang:latest
-RUN mkdir /app 
-WORKDIR /app 
-ENV SRC_DIR=/go/src/github.com/codeskyblue/gohttpserver
-ADD . $SRC_DIR
-RUN cd $SRC_DIR; go build; cp gohttpserver /app/
-ENTRYPOINT ["/app/gohttpserver"]
+FROM golang:1.9 AS build
+WORKDIR /go/src/github.com/codeskyblue/gohttpserver
+ADD . /go/src/github.com/codeskyblue/gohttpserver/
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o gohttpserver .
+
+FROM alpine:3.6
+WORKDIR /app
+RUN mkdir -p /app/public
+VOLUME /app/public
+ADD res ./res
+COPY --from=build /go/src/github.com/codeskyblue/gohttpserver/gohttpserver .
+EXPOSE 8000
+CMD ["/app/gohttpserver", "--root=/app/public"]