diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index c59088e..be36914 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -12,7 +12,7 @@ jobs:
   build-and-test:
     strategy:
       matrix:
-        go-version: ['1.19', '1.20', '1.21']
+        go-version: ['1.18', '1.20', '1.21']
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
 
diff --git a/go.mod b/go.mod
index 056b0b7..589e794 100644
--- a/go.mod
+++ b/go.mod
@@ -1,5 +1,5 @@
 module github.com/tklauser/numcpus
 
-go 1.13
+go 1.18
 
 require golang.org/x/sys v0.15.0
diff --git a/numcpus_linux.go b/numcpus_linux.go
index 1a30525..7e75cb0 100644
--- a/numcpus_linux.go
+++ b/numcpus_linux.go
@@ -15,7 +15,6 @@
 package numcpus
 
 import (
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -35,7 +34,7 @@ func getFromCPUAffinity() (int, error) {
 }
 
 func readCPURange(file string) (int, error) {
-	buf, err := ioutil.ReadFile(filepath.Join(sysfsCPUBasePath, file))
+	buf, err := os.ReadFile(filepath.Join(sysfsCPUBasePath, file))
 	if err != nil {
 		return 0, err
 	}
@@ -48,16 +47,16 @@ func parseCPURange(cpus string) (int, error) {
 		if len(cpuRange) == 0 {
 			continue
 		}
-		rangeOp := strings.SplitN(cpuRange, "-", 2)
-		first, err := strconv.ParseUint(rangeOp[0], 10, 32)
+		from, to, found := strings.Cut(cpuRange, "-")
+		first, err := strconv.ParseUint(from, 10, 32)
 		if err != nil {
 			return 0, err
 		}
-		if len(rangeOp) == 1 {
+		if !found {
 			n++
 			continue
 		}
-		last, err := strconv.ParseUint(rangeOp[1], 10, 32)
+		last, err := strconv.ParseUint(to, 10, 32)
 		if err != nil {
 			return 0, err
 		}
@@ -89,7 +88,7 @@ func getConfigured() (int, error) {
 }
 
 func getKernelMax() (int, error) {
-	buf, err := ioutil.ReadFile(filepath.Join(sysfsCPUBasePath, "kernel_max"))
+	buf, err := os.ReadFile(filepath.Join(sysfsCPUBasePath, "kernel_max"))
 	if err != nil {
 		return 0, err
 	}
diff --git a/numcpus_linux_test.go b/numcpus_linux_test.go
index 0ba9929..0a6a8ec 100644
--- a/numcpus_linux_test.go
+++ b/numcpus_linux_test.go
@@ -18,37 +18,39 @@ import "testing"
 
 func TestParseCPURange(t *testing.T) {
 	testCases := []struct {
-		cpus string
-		n    int
+		str     string
+		n       int
+		wantErr bool
 	}{
-		{"", 0},
-		{"0", 1},
-		{"0-1", 2},
-		{"0-7", 8},
-		{"1-7", 7},
-		{"1-15", 15},
-		{"0-3,7", 5},
-		{"0,2-4", 4},
-		{"0,2-4,7", 5},
-		{"0,2-4,7-15", 13},
+		{str: "", n: 0},
+		{str: "0", n: 1},
+		{str: "0-1", n: 2},
+		{str: "0-7", n: 8},
+		{str: "1-7", n: 7},
+		{str: "1-15", n: 15},
+		{str: "0-3,7", n: 5},
+		{str: "0,2-4", n: 4},
+		{str: "0,2-4,7", n: 5},
+		{str: "0,2-4,7-15", n: 13},
+		{str: "0,2-4,6,8-10", n: 8},
+		{str: "invalid", n: 0, wantErr: true},
+		{str: "0-", n: 0, wantErr: true},
+		{str: "0-,1", n: 0, wantErr: true},
+		{str: "0,-3,5", n: 0, wantErr: true},
 	}
 
 	for _, tc := range testCases {
-		n, err := parseCPURange(tc.cpus)
-		if err != nil {
-			t.Errorf("failed to parse CPU range: %v", err)
+		n, err := parseCPURange(tc.str)
+		if !tc.wantErr && err != nil {
+			t.Errorf("parseCPURange(%q) = %v, expected no error", tc.str, err)
+		} else if tc.wantErr && err == nil {
+			t.Errorf("parseCPURange(%q) expected error", tc.str)
 		}
 
 		if n != tc.n {
-			t.Errorf("parseCPURange(%q) = %d, expected %d", tc.cpus, n, tc.n)
+			t.Errorf("parseCPURange(%q) = %d, expected %d", tc.str, n, tc.n)
 		}
 	}
-
-	str := "invalid"
-	_, err := parseCPURange(str)
-	if err == nil {
-		t.Errorf("parseCPURange(%q) unexpectedly succeeded", str)
-	}
 }
 
 func TestGetFromCPUAffinity(t *testing.T) {