Use alpine latest

Dockerfile

@@ -17,7 +17,7 @@ RUN set -e ;\
     CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
     go build -a -installsuffix cgo -o /go/bin/app
 
-FROM alpine:3.11.6
+FROM alpine:latest
 RUN apk add --update --no-cache ca-certificates
 COPY --from=build-env /go/bin/app /go/bin/app
 ADD ./configs/default.json /models/default.json