diff --git a/.github/workflows/golangci-lint.yml b/.github/workflows/golangci-lint.yml
index 1ddfe1a..fd813bb 100644
--- a/.github/workflows/golangci-lint.yml
+++ b/.github/workflows/golangci-lint.yml
@@ -11,14 +11,14 @@ jobs:
     name: lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Setup Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version-file: go.mod
           check-latest: true
       - name: golangci-lint
-        uses: golangci/golangci-lint-action@v3
+        uses: golangci/golangci-lint-action@v9.2.0
         with:
-          version: v1.50
+          version: v2.11.4
diff --git a/clip/clip.go b/clip/clip.go
index b64fda3..765969c 100644
--- a/clip/clip.go
+++ b/clip/clip.go
@@ -91,10 +91,7 @@ func ring(box orb.Bound, in orb.Ring) orb.Ring {
 	f := in[0]
 	l := in[len(in)-1]
 
-	initClosed := false
-	if f == l {
-		initClosed = true
-	}
+	initClosed := f == l
 
 	for edge := 1; edge <= 8; edge <<= 1 {
 		out = out[:0]
@@ -150,9 +147,11 @@ func ring(box orb.Bound, in orb.Ring) orb.Ring {
 }
 
 // bitCode returns the point position relative to the bbox:
-//         left  mid  right
-//    top  1001  1000  1010
-//    mid  0001  0000  0010
+//
+//	     left  mid  right
+//	top  1001  1000  1010
+//	mid  0001  0000  0010
+//
 // bottom  0101  0100  0110
 func bitCode(b orb.Bound, p orb.Point) int {
 	code := 0
diff --git a/encoding/ewkb/ewkb_test.go b/encoding/ewkb/ewkb_test.go
index 5d1dbee..10dcdb3 100644
--- a/encoding/ewkb/ewkb_test.go
+++ b/encoding/ewkb/ewkb_test.go
@@ -4,7 +4,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/hex"
-	"io/ioutil"
+	"io"
 	"testing"
 
 	"github.com/paulmach/orb"
@@ -37,7 +37,7 @@ func MustDecodeHex(s string) []byte {
 
 func BenchmarkEncode_Point(b *testing.B) {
 	g := orb.Point{1, 2}
-	e := NewEncoder(ioutil.Discard)
+	e := NewEncoder(io.Discard)
 
 	b.ReportAllocs()
 	b.ResetTimer()
@@ -54,7 +54,7 @@ func BenchmarkEncode_LineString(b *testing.B) {
 		{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5},
 		{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5},
 	}
-	e := NewEncoder(ioutil.Discard)
+	e := NewEncoder(io.Discard)
 
 	b.ReportAllocs()
 	b.ResetTimer()
diff --git a/encoding/internal/wkbcommon/wkb.go b/encoding/internal/wkbcommon/wkb.go
index 515802e..415786b 100644
--- a/encoding/internal/wkbcommon/wkb.go
+++ b/encoding/internal/wkbcommon/wkb.go
@@ -284,11 +284,12 @@ func readByteOrderType(r io.Reader, buf []byte) (byteOrder, uint32, int, error)
 	}
 
 	var order byteOrder
-	if buf[0] == 0 {
+	switch buf[0] {
+	case 0:
 		order = bigEndian
-	} else if buf[0] == 1 {
+	case 1:
 		order = littleEndian
-	} else {
+	default:
 		return 0, 0, 0, ErrNotWKB
 	}
 
diff --git a/encoding/mvt/marshal_test.go b/encoding/mvt/marshal_test.go
index e30812d..2c14d8c 100644
--- a/encoding/mvt/marshal_test.go
+++ b/encoding/mvt/marshal_test.go
@@ -4,8 +4,8 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"math"
+	"os"
 	"reflect"
 	"testing"
 
@@ -388,7 +388,7 @@ func comparePoints(t testing.TB, e, r []orb.Point, xEpsilon, yEpsilon float64) {
 }
 
 func loadMVT(t testing.TB, tile maptile.Tile) []byte {
-	data, err := ioutil.ReadFile(fmt.Sprintf("testdata/%d-%d-%d.mvt", tile.Z, tile.X, tile.Y))
+	data, err := os.ReadFile(fmt.Sprintf("testdata/%d-%d-%d.mvt", tile.Z, tile.X, tile.Y))
 	if err != nil {
 		t.Fatalf("failed to load mvt file: %v", err)
 	}
@@ -397,7 +397,7 @@ func loadMVT(t testing.TB, tile maptile.Tile) []byte {
 }
 
 func loadGeoJSON(t testing.TB, tile maptile.Tile) map[string]*geojson.FeatureCollection {
-	data, err := ioutil.ReadFile(fmt.Sprintf("testdata/%d-%d-%d.json", tile.Z, tile.X, tile.Y))
+	data, err := os.ReadFile(fmt.Sprintf("testdata/%d-%d-%d.json", tile.Z, tile.X, tile.Y))
 	if err != nil {
 		t.Fatalf("failed to load mvt file: %v", err)
 	}
diff --git a/encoding/mvt/unmarshal.go b/encoding/mvt/unmarshal.go
index 7454850..7749419 100644
--- a/encoding/mvt/unmarshal.go
+++ b/encoding/mvt/unmarshal.go
@@ -5,7 +5,7 @@ import (
 	"compress/gzip"
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 
 	"github.com/paulmach/orb"
 	"github.com/paulmach/orb/encoding/mvt/vectortile"
@@ -23,7 +23,7 @@ func UnmarshalGzipped(data []byte) (Layers, error) {
 		return nil, fmt.Errorf("failed to create gzreader: %v", err)
 	}
 
-	decoded, err := ioutil.ReadAll(gzreader)
+	decoded, err := io.ReadAll(gzreader)
 	if err != nil {
 		return nil, fmt.Errorf("failed to unzip: %v", err)
 	}
diff --git a/encoding/wkb/wkb_test.go b/encoding/wkb/wkb_test.go
index 460307d..44e41c7 100644
--- a/encoding/wkb/wkb_test.go
+++ b/encoding/wkb/wkb_test.go
@@ -3,7 +3,7 @@ package wkb
 import (
 	"bytes"
 	"encoding/binary"
-	"io/ioutil"
+	"io"
 	"testing"
 
 	"github.com/paulmach/orb"
@@ -27,7 +27,7 @@ func TestMustMarshal(t *testing.T) {
 
 func BenchmarkEncode_Point(b *testing.B) {
 	g := orb.Point{1, 2}
-	e := NewEncoder(ioutil.Discard)
+	e := NewEncoder(io.Discard)
 
 	b.ReportAllocs()
 	b.ResetTimer()
@@ -44,7 +44,7 @@ func BenchmarkEncode_LineString(b *testing.B) {
 		{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5},
 		{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5},
 	}
-	e := NewEncoder(ioutil.Discard)
+	e := NewEncoder(io.Discard)
 
 	b.ReportAllocs()
 	b.ResetTimer()
diff --git a/encoding/wkt/benchmarks_test.go b/encoding/wkt/benchmarks_test.go
index fd48ec0..07339ce 100644
--- a/encoding/wkt/benchmarks_test.go
+++ b/encoding/wkt/benchmarks_test.go
@@ -2,7 +2,7 @@ package wkt
 
 import (
 	"encoding/json"
-	"io/ioutil"
+	"os"
 	"testing"
 
 	"github.com/paulmach/orb"
@@ -103,7 +103,7 @@ func BenchmarkUnmarshalMultiPolygon(b *testing.B) {
 }
 
 func loadJSON(tb testing.TB, filename string, obj interface{}) {
-	data, err := ioutil.ReadFile(filename)
+	data, err := os.ReadFile(filename)
 	if err != nil {
 		tb.Fatalf("failed to load mvt file: %v", err)
 	}
diff --git a/geo/area.go b/geo/area.go
index 4cf5d17..f36f509 100644
--- a/geo/area.go
+++ b/geo/area.go
@@ -56,19 +56,20 @@ func ringArea(r orb.Ring) float64 {
 
 	area := 0.0
 	for i := 0; i < l; i++ {
-		if i == l-3 { // i = N-3
+		switch i {
+		case l - 3: // i = N-3
 			lo = l - 3
 			mi = l - 2
 			hi = 0
-		} else if i == l-2 { // i = N-2
+		case l - 2: // i = N-2
 			lo = l - 2
 			mi = 0
 			hi = 0
-		} else if i == l-1 { // i = N-1
+		case l - 1: // i = N-1
 			lo = 0
 			mi = 0
 			hi = 1
-		} else { // i = 0 to N-3
+		default: // i = 0 to N-3
 			lo = i
 			mi = i + 1
 			hi = i + 2
diff --git a/geojson/feature_test.go b/geojson/feature_test.go
index a976448..0fefc70 100644
--- a/geojson/feature_test.go
+++ b/geojson/feature_test.go
@@ -3,7 +3,7 @@ package geojson
 import (
 	"bytes"
 	"encoding/json"
-	"io/ioutil"
+	"os"
 	"reflect"
 	"strings"
 	"testing"
@@ -424,7 +424,7 @@ func TestFeature_MarshalBSON_extraMembers(t *testing.T) {
 // }
 
 func BenchmarkFeatureMarshalJSON(b *testing.B) {
-	data, err := ioutil.ReadFile("../encoding/mvt/testdata/16-17896-24449.json")
+	data, err := os.ReadFile("../encoding/mvt/testdata/16-17896-24449.json")
 	if err != nil {
 		b.Fatalf("could not open file: %v", err)
 	}
@@ -446,7 +446,7 @@ func BenchmarkFeatureMarshalJSON(b *testing.B) {
 }
 
 func BenchmarkFeatureUnmarshalJSON(b *testing.B) {
-	data, err := ioutil.ReadFile("../encoding/mvt/testdata/16-17896-24449.json")
+	data, err := os.ReadFile("../encoding/mvt/testdata/16-17896-24449.json")
 	if err != nil {
 		b.Fatalf("could not open file: %v", err)
 	}
@@ -463,7 +463,7 @@ func BenchmarkFeatureUnmarshalJSON(b *testing.B) {
 }
 
 func BenchmarkFeatureMarshalBSON(b *testing.B) {
-	data, err := ioutil.ReadFile("../encoding/mvt/testdata/16-17896-24449.json")
+	data, err := os.ReadFile("../encoding/mvt/testdata/16-17896-24449.json")
 	if err != nil {
 		b.Fatalf("could not open file: %v", err)
 	}
@@ -485,7 +485,7 @@ func BenchmarkFeatureMarshalBSON(b *testing.B) {
 }
 
 func BenchmarkFeatureUnmarshalBSON(b *testing.B) {
-	data, err := ioutil.ReadFile("../encoding/mvt/testdata/16-17896-24449.json")
+	data, err := os.ReadFile("../encoding/mvt/testdata/16-17896-24449.json")
 	if err != nil {
 		b.Fatalf("could not open file: %v", err)
 	}
diff --git a/go.mod b/go.mod
index 8f99949..186da82 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/paulmach/orb
 
-go 1.15
+go 1.25
 
 require (
 	github.com/gogo/protobuf v1.3.2
diff --git a/go.sum b/go.sum
index d1a75cb..7dcd0ae 100644
--- a/go.sum
+++ b/go.sum
@@ -11,10 +11,8 @@ github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/klauspost/compress v1.13.6/go.mod h1:/3/Vjq9QcHkK5uEr5lBEmyoZ1iFhe47etQ6QUkpK6sk=
-github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
-github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/montanaflynn/stats v0.0.0-20171201202039-1bf9dbcd8cbe/go.mod h1:wL8QJuTMNUDYhXwkmfOly8iTdp5TEcJFWZD2D7SIkUc=
 github.com/paulmach/protoscan v0.2.1 h1:rM0FpcTjUMvPUNk2BhPJrreDKetq43ChnL+x1sRg8O8=
@@ -68,13 +66,11 @@ golang.org/x/tools v0.0.0-20210106214847-113979e3529a/go.mod h1:emZCQorbCU4vsT4f
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
 google.golang.org/protobuf v1.27.1 h1:SnqbnDw1V7RiZcXPx5MEeqPv2s79L9i7BJUlG/+RurQ=
 google.golang.org/protobuf v1.27.1/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
diff --git a/maptile/tile.go b/maptile/tile.go
index 1e61bd3..2a4488b 100644
--- a/maptile/tile.go
+++ b/maptile/tile.go
@@ -228,9 +228,12 @@ func (t Tile) Children() Tiles {
 
 // ChildrenInZoomRange returns all the children tiles of tile from ranges [zoomStart, zoomEnd], both ends inclusive.
 func ChildrenInZoomRange(tile Tile, zoomStart, zoomEnd Zoom) Tiles {
+	//nolint:staticcheck // clearer this way
 	if !(zoomStart <= zoomEnd) {
 		panic("zoomStart must be <= zoomEnd")
 	}
+
+	//nolint:staticcheck // clearer this way
 	if !(tile.Z <= zoomStart) {
 		panic("tile.Z is must be <= zoomStart")
 	}
diff --git a/maptile/tilecover/cover_test.go b/maptile/tilecover/cover_test.go
index ff33496..ae7a91a 100644
--- a/maptile/tilecover/cover_test.go
+++ b/maptile/tilecover/cover_test.go
@@ -2,8 +2,8 @@ package tilecover
 
 import (
 	"encoding/json"
-	"io/ioutil"
 	"math"
+	"os"
 	"sort"
 	"strings"
 	"testing"
@@ -92,7 +92,7 @@ func TestTestdata(t *testing.T) {
 
 			// ts := Geometry(f.Geometry, tc.max)
 			// blob, _ := json.MarshalIndent(MergeUp(ts, tc.min).ToFeatureCollection(), "", "  ")
-			// ioutil.WriteFile("./testdata/"+tc.name+"_out.geojson", blob, 0644)
+			// os.WriteFile("./testdata/"+tc.name+"_out.geojson", blob, 0644)
 
 			expected := loadFeatureCollection(t, "./testdata/"+tc.name+"_out.geojson")
 
@@ -108,7 +108,7 @@ func TestTestdata(t *testing.T) {
 }
 
 func TestCountries(t *testing.T) {
-	files, err := ioutil.ReadDir("./testdata/world")
+	files, err := os.ReadDir("./testdata/world")
 	if err != nil {
 		t.Errorf("could not read directory: %v", err)
 	}
@@ -182,7 +182,7 @@ func sortFC(fc *geojson.FeatureCollection) {
 
 func loadFeature(t testing.TB, path string) *geojson.Feature {
 	t.Helper()
-	data, err := ioutil.ReadFile(path)
+	data, err := os.ReadFile(path)
 	if err != nil {
 		t.Fatalf("unable to read file: %v", err)
 	}
@@ -210,7 +210,7 @@ func loadFeature(t testing.TB, path string) *geojson.Feature {
 
 func loadFeatureCollection(t testing.TB, path string) *geojson.FeatureCollection {
 	t.Helper()
-	data, err := ioutil.ReadFile(path)
+	data, err := os.ReadFile(path)
 	if err != nil {
 		t.Fatalf("unable to read file: %v", err)
 	}
@@ -250,7 +250,7 @@ func output(t testing.TB, name string, r *geojson.FeatureCollection) {
 		t.Fatalf("error marshalling json: %v", err)
 	}
 
-	err = ioutil.WriteFile("failure_"+name+".geojson", data, 0644)
+	err = os.WriteFile("failure_"+name+".geojson", data, 0644)
 	if err != nil {
 		t.Fatalf("write file failure: %v", err)
 	}
diff --git a/planar/contains.go b/planar/contains.go
index fbfc455..1d5cc53 100644
--- a/planar/contains.go
+++ b/planar/contains.go
@@ -66,7 +66,8 @@ func rayIntersect(p, s, e orb.Point) (intersects, on bool) {
 		s, e = e, s
 	}
 
-	if p[0] == s[0] {
+	switch p[0] {
+	case s[0]:
 		if p[1] == s[1] {
 			// p == start
 			return false, true
@@ -84,7 +85,7 @@ func rayIntersect(p, s, e orb.Point) (intersects, on bool) {
 
 		// Move the y coordinate to deal with degenerate case
 		p[0] = math.Nextafter(p[0], math.Inf(1))
-	} else if p[0] == e[0] {
+	case e[0]:
 		if p[1] == e[1] {
 			// matching the end point
 			return false, true
diff --git a/simplify/benchmarks_test.go b/simplify/benchmarks_test.go
index 14d043f..cdff2fa 100644
--- a/simplify/benchmarks_test.go
+++ b/simplify/benchmarks_test.go
@@ -164,7 +164,11 @@ func benchmarkData() orb.LineString {
 	if err != nil {
 		panic(err)
 	}
-	defer f.Close()
+	defer func() {
+		if err := f.Close(); err != nil {
+			panic(err)
+		}
+	}()
 
 	var points []float64
 	err = json.NewDecoder(f).Decode(&points)