Update Dockerfile: add tzdata

Dockerfile

@@ -1,16 +1,15 @@
 FROM golang:1.10.3-alpine3.7 as builder
 RUN \
-    apk update && \
-    apk add --no-cache git ca-certificates make && \
     cd / && \
+    apk update && \
+    apk add --no-cache git ca-certificates make tzdata && \
     git clone https://github.com/inCaller/prometheus_bot && \
     cd prometheus_bot && \
     go get -d -v && \
     CGO_ENABLED=0 GOOS=linux go build -v -a -installsuffix cgo -o prometheus_bot 
 
-
 FROM alpine:3.7
 COPY --from=builder /prometheus_bot/prometheus_bot /
-RUN apk add --no-cache ca-certificates
+RUN apk add --no-cache ca-certificates tzdata
 EXPOSE 9087
 ENTRYPOINT ["/prometheus_bot"]