Update base image, minor tweaks

Dockerfile

@@ -1,10 +1,10 @@
-FROM golang:1.12.6-alpine3.9 AS build
+FROM golang:1.14.7-alpine3.12 AS build
 
 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-201906
+FROM quay.io/ntppool/dnsmapper:geoip-data-202007
 USER root
 RUN apk --no-cache add ca-certificates
 

geoipapi.go

@@ -84,7 +84,7 @@ func getCity(req *http.Request) (*geoip2.City, error) {
 	ipStr := req.FormValue("ip")
 	ip := net.ParseIP(ipStr)
 	if ip == nil {
-		return nil, fmt.Errorf("Missing IP")
+		return nil, fmt.Errorf("missing IP address")
 	}
 	return getCityIP(ip)
 }