Upgrade dependencies, prepare to use geoipupdate to update data

Dockerfile

@@ -1,10 +1,11 @@
-FROM golang:1.14.7-alpine3.12 AS build
+FROM golang:1.18-alpine3.15 AS build
+RUN apk --no-cache add git
 
 WORKDIR /go/src/github.com/abh/geoipapi
 ADD . /go/src/github.com/abh/geoipapi
 RUN go install -v ./...
 
-FROM quay.io/ntppool/dnsmapper:geoip-data-202007
+FROM alpine:3.15
 USER root
 RUN apk --no-cache add ca-certificates
 
@@ -12,6 +13,8 @@ RUN addgroup geoip && adduser -D -G geoip geoip
 WORKDIR /geoip/
 COPY --from=build /go/bin/geoipapi  /bin/
 
+ADD start.sh /start.sh
+
 USER geoip
 
-CMD ["/bin/geoipapi"]
+CMD ["/start.sh"]