update Dockerfile

Dockerfile

@@ -1,12 +1,15 @@
-FROM alpine:latest
+FROM golang:1.18-alpine3.16 AS base
+
+WORKDIR /app
+
+COPY . .
+
+RUN go mod tidy && go build -o nsq_exporter .
+
+FROM alpine:3.16
 
 EXPOSE 9117
 
-ENV  GOPATH /go
+COPY --from=base /app/nsq_exporter /nsq_exporter
-ENV APPPATH $GOPATH/src/github.com/lovoo/nsq_exporter
-COPY . $APPPATH
-RUN apk add --update -t build-deps go git mercurial libc-dev gcc libgcc \
-    && cd $APPPATH && go get -d && go build -o /nsq_exporter \
-    && apk del --purge build-deps && rm -rf $GOPATH
 
 ENTRYPOINT ["/nsq_exporter"]