Replace ErrNotFound constant with errors.New for consistent error handling

geoip2.go

@@ -2,13 +2,14 @@ package geoip2
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net/netip"
 	"strings"
 )
 
 // ErrNotFound is returned when the database does not contain the IP address.
-const ErrNotFound = "not found"
+var ErrNotFound = errors.New("not found")
 
 // Info is a structure that contains information about the IP address.
 type Info struct {

service/maxmind/mmdb/city.go

@@ -1,7 +1,6 @@
 package mmdb
 
 import (
-	"errors"
 	"net/netip"
 
 	"git.kor-elf.net/kor-elf-shield/geoip2"
@@ -19,7 +18,7 @@ const (
 // City is a structure that contains information about the IP address.
 type City struct {
 	// lang is a language.
-	lang language
+	lang Language
 }
 
 // NewCity creates a new City instance.
@@ -27,7 +26,7 @@ type City struct {
 // @param logger - a logger
 // @param dir - a directory for storing MaxMind GeoIP2 database
 // @return geoip2.RefreshableGeoIP2 - a MaxMind GeoIP2 database service
-func NewCity(download *Download, logger geoip2.Logger, dir string, language language) geoip2.RefreshableGeoIP2 {
+func NewCity(download *Download, logger geoip2.Logger, dir string, language Language) geoip2.RefreshableGeoIP2 {
 	city := &City{
 		lang: language,
 	}
@@ -47,7 +46,7 @@ func (c *City) infoCity(ip netip.Addr, reader *oschwaldGeoip2.Reader) (geoip2.In
 		return geoip2.Info{}, err
 	}
 	if !record.HasData() {
-		return geoip2.Info{}, errors.New(geoip2.ErrNotFound)
+		return geoip2.Info{}, geoip2.ErrNotFound
 	}
 
 	var timeZone string

service/maxmind/mmdb/mmdb.go

@@ -1,15 +1,15 @@
 package mmdb
 
-type language string
+type Language string
 
 const (
-	LanguageRussian  = language("Russian")
-	LanguageEnglish  = language("English")
-	LanguageSpanish  = language("Spanish")
-	LanguageFrench   = language("French")
-	LanguageGerman   = language("German")
-	LanguageJapanese = language("Japanese")
+	LanguageRussian  = Language("Russian")
+	LanguageEnglish  = Language("English")
+	LanguageSpanish  = Language("Spanish")
+	LanguageFrench   = Language("French")
+	LanguageGerman   = Language("German")
+	LanguageJapanese = Language("Japanese")
 
-	LanguageBrazilianPortuguese = language("BrazilianPortuguese")
-	LanguageSimplifiedChinese   = language("SimplifiedChinese")
+	LanguageBrazilianPortuguese = Language("BrazilianPortuguese")
+	LanguageSimplifiedChinese   = Language("SimplifiedChinese")
 )