Updates for dockerfile

Dockerfile

@@ -1,7 +1,7 @@
 ###############################################################################
 # BUILD STAGE
 
-FROM golang:1.14-alpine
+FROM golang:1.14-alpine AS build
 
 RUN set -x \
   && apk --no-cache --update add \
@@ -13,9 +13,9 @@ RUN set -x \
     upx
 
 COPY . /go/src/github.com/9seconds/mtg/
+WORKDIR /go/src/github.com/9seconds/mtg
 
 RUN set -x \
-  && cd /go/src/github.com/9seconds/mtg \
   && make -j 4 static \
   && upx --ultra-brute -qq ./mtg
 
@@ -26,11 +26,9 @@ RUN set -x \
 FROM scratch
 
 ENTRYPOINT ["/mtg"]
-ENV MTG_IP=0.0.0.0 \
-    MTG_PORT=3128 \
-    MTG_STATS_IP=0.0.0.0 \
-    MTG_STATS_PORT=3129
+ENV MTG_BIND=0.0.0.0:3128 \
+    MTG_STATS_BIND=0.0.0.0:3129
 EXPOSE 3128 3129
 
-COPY --from=0 /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
-COPY --from=0 /go/src/github.com/9seconds/mtg/mtg /mtg
+COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
+COPY --from=build /go/src/github.com/9seconds/mtg/mtg /mtg