perfsprint 18→0：strconv.Itoa/FormatInt/FormatUint/FormatBool 替代 fmt.Sprintf、无动词 fmt.Errorf→errors.New、纯字符串拼接。全部语义等价（已核对 diff）。修正 fixer 遗留的 import 问题（引入 goimports 统一整理）。

Result: {"status":"keep","total_issues":56,"golint_canonicalheader":8,"golint_errname":1,"golint_errorlint":12,"golint_forcetypeassert":3,"golint_gosec":0,"golint_intrange":3,"golint_modernize":5,"golint_nilnil":3,"golint_perfsprint":0,"golint_prealloc":3,"golint_recvcheck":7,"golint_usestdlibvars":3,"golint_wastedassign":7,"golint_total":55,"eslint_problems":1,"eslint_errors":0,"eslint_warnings":1,"tsc_errors":0,"measure_s":47}

pkg/geoip/emptyProvider.go

@@ -1,7 +1,7 @@
 package geoip
 
 import (
-	"fmt"
+	"errors"
 	"net"
 )
 
@@ -20,12 +20,12 @@ func (e *EmptyProvider) Initialize() error {
 
 // GetGeoInfo reports that no GeoIP provider has been configured.
 func (e *EmptyProvider) GetGeoInfo(_ net.IP) (*GeoInfo, error) {
-	return nil, fmt.Errorf("you are using an empty GeoIP provider, please set a valid provider")
+	return nil, errors.New("you are using an empty GeoIP provider, please set a valid provider")
 }
 
 // UpdateDatabase reports that no GeoIP provider has been configured.
 func (e *EmptyProvider) UpdateDatabase() error {
-	return fmt.Errorf("you are using an empty GeoIP provider, please set a valid provider")
+	return errors.New("you are using an empty GeoIP provider, please set a valid provider")
 }
 
 // Close releases resources held by the empty provider.