Update Dockerfile (#39)

Set up a proxy for Go

Dockerfile

@@ -1,17 +1,22 @@
 FROM golang:alpine AS builder
 
 WORKDIR /app
+COPY . .
 
-ADD . .
+ENV GO111MODULE=on GOPROXY=https://goproxy.cn,direct
+RUN go mod download
 
-RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o override
+RUN CGO_ENABLED=0 go build -ldflags="-w -s" -o override
 
 FROM alpine:latest
 
-COPY --from=builder /app/override /usr/local/bin/override
+RUN apk --no-cache add ca-certificates
 
-WORKDIR /app
+COPY --from=builder /app/override /usr/local/bin/
+COPY config.json.example /app/config.json
 
-ENTRYPOINT ["/usr/local/bin/override"]
+WORKDIR /app
+VOLUME /app
 
-EXPOSE 8181
+EXPOSE 8080
+CMD ["override"]