Updates for new golangci-lint

.golangci.toml

@@ -25,9 +25,6 @@ disable = [
     # We don't follow its policy about not defining dynamic errors.
     "err113",
 
-    # This doesn't seem to know about CTEs or DELETEs with RETURNING
-    "execinquery",
-
     # We often don't initialize all of the struct fields. This is fine
     # generally
     "exhaustruct",
@@ -51,9 +48,6 @@ disable = [
     "gocognit",
     "godox",
 
-    # We have to disable both "gomnd" and "mnd" temporarily, apparently.
-    "gomnd",
-
     # This only "caught" one thing, and it seemed like a reasonable use
     # of Han script. Generally, I don't think we want to prevent the use
     # of particular scripts. The time.Local checks might be useful, but

client/client.go

@@ -10,6 +10,8 @@ import (
 // Client downloads GeoIP2 and GeoLite2 MMDB databases.
 //
 // After creation, it is valid for concurrent use.
+//
+//nolint:recvcheck // changing this would be a breaking change.
 type Client struct {
 	accountID  int
 	endpoint   string

internal/geoipupdate/database/reader.go

@@ -23,14 +23,18 @@ type ReadResult struct {
 }
 
 // MarshalJSON is a custom json marshaler that strips out zero time fields.
-func (r ReadResult) MarshalJSON() ([]byte, error) {
+func (r *ReadResult) MarshalJSON() ([]byte, error) {
+	if r == nil {
+		return []byte("null"), nil
+	}
+
 	type partialResult ReadResult
 	s := &struct {
 		partialResult
 		ModifiedAt int64 `json:"modified_at,omitempty"`
 		CheckedAt  int64 `json:"checked_at,omitempty"`
 	}{
-		partialResult: partialResult(r),
+		partialResult: partialResult(*r),
 		ModifiedAt:    0,
 		CheckedAt:     0,
 	}

internal/geoipupdate/geoip_updater_test.go

@@ -283,7 +283,7 @@ func (w *mockWriter) Write(
 	return nil
 }
 
-func (w mockWriter) GetHash(editionID string) (string, error) {
+func (w *mockWriter) GetHash(editionID string) (string, error) {
 	return w.md5s[editionID], nil
 }