diff --git a/bootstrap/cache/disk_cache.go b/bootstrap/cache/disk_cache.go
index 3477f02..613f526 100644
--- a/bootstrap/cache/disk_cache.go
+++ b/bootstrap/cache/disk_cache.go
@@ -7,7 +7,6 @@ package cache
 import (
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"time"
@@ -98,7 +97,7 @@ func (d *DiskCache) Save(filename string, data []byte) error {
 		return err
 	}
 
-	err = ioutil.WriteFile(d.cacheDirPath(filename), data, 0664)
+	err = os.WriteFile(d.cacheDirPath(filename), data, 0664)
 	if err != nil {
 		return err
 	}
@@ -126,7 +125,7 @@ func (d *DiskCache) Load(filename string) ([]byte, error) {
 	}
 
 	var bytes []byte
-	bytes, err = ioutil.ReadFile(d.cacheDirPath(filename))
+	bytes, err = os.ReadFile(d.cacheDirPath(filename))
 
 	if err != nil {
 		return nil, err
diff --git a/bootstrap/cache/disk_cache_test.go b/bootstrap/cache/disk_cache_test.go
index 3290738..5106624 100644
--- a/bootstrap/cache/disk_cache_test.go
+++ b/bootstrap/cache/disk_cache_test.go
@@ -6,7 +6,6 @@ package cache
 
 import (
 	"bytes"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -14,14 +13,14 @@ import (
 )
 
 func TestDiskCache(t *testing.T) {
-	dir, err := ioutil.TempDir("", "test")
+	dir, err := os.MkdirTemp("", "test")
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(dir)
 
 	rdapDir := filepath.Join(dir, ".openrdap")
-	
+
 	m1 := NewDiskCache()
 	m1.Dir = rdapDir
 
@@ -101,4 +100,3 @@ func TestDiskCache(t *testing.T) {
 		t.Fatalf("loaded2(%v) != asn2(%v)", loaded2, asn2)
 	}
 }
-
diff --git a/bootstrap/client.go b/bootstrap/client.go
index 4daadbe..bdd4ac9 100644
--- a/bootstrap/client.go
+++ b/bootstrap/client.go
@@ -14,36 +14,38 @@
 // files.
 //
 // Basic usage:
-//   question := &bootstrap.Question{
-//     RegistryType: bootstrap.DNS,
-//     Query: "example.cz",
-//   }
 //
-//   b := &bootstrap.Client{}
+//	question := &bootstrap.Question{
+//	  RegistryType: bootstrap.DNS,
+//	  Query: "example.cz",
+//	}
 //
-//   var answer *bootstrap.Answer
-//   answer, err := b.Lookup(question)
+//	b := &bootstrap.Client{}
 //
-//   if err == nil {
-//     for _, url := range answer.URLs {
-//       fmt.Println(url)
-//     }
-//   }
+//	var answer *bootstrap.Answer
+//	answer, err := b.Lookup(question)
+//
+//	if err == nil {
+//	  for _, url := range answer.URLs {
+//	    fmt.Println(url)
+//	  }
+//	}
 //
 // Download and list the contents of the DNS Service Registry:
-//   b := &bootstrap.Client{}
 //
-//   // Before you can use a Registry, you need to download it first.
-//   err := b.Download(bootstrap.DNS) // Downloads https://data.iana.org/rdap/dns.json.
+//	b := &bootstrap.Client{}
+//
+//	// Before you can use a Registry, you need to download it first.
+//	err := b.Download(bootstrap.DNS) // Downloads https://data.iana.org/rdap/dns.json.
 //
-//   if err == nil {
-//     var dns *DNSRegistry = b.DNS()
+//	if err == nil {
+//	  var dns *DNSRegistry = b.DNS()
 //
-//     // Print TLDs with RDAP service.
-//     for tld, _ := range dns.File().Entries {
-//       fmt.Println(tld)
-//     }
-//   }
+//	  // Print TLDs with RDAP service.
+//	  for tld, _ := range dns.File().Entries {
+//	    fmt.Println(tld)
+//	  }
+//	}
 //
 // You can configure bootstrap.Client{} with a custom http.Client, base URL
 // (default https://data.iana.org/rdap), and custom cache. bootstrap.Question{}
@@ -68,16 +70,16 @@
 //
 // Disk cache usage:
 //
-//   b := bootstrap.NewClient()
-//   b.Cache = cache.NewDiskCache()
+//	b := &bootstrap.Client{}
+//	b.Cache = cache.NewDiskCache()
 //
-//   dsr := b.DNS()  // Tries to load dns.json from disk cache, doesn't exist yet, so returns nil.
-//   b.Download(bootstrap.DNS) // Downloads dns.json, saves to disk cache.
+//	dsr := b.DNS()  // Tries to load dns.json from disk cache, doesn't exist yet, so returns nil.
+//	b.Download(bootstrap.DNS) // Downloads dns.json, saves to disk cache.
 //
-//   b2 := bootstrap.NewClient()
-//   b2.Cache = cache.NewDiskCache()
+//	b2 := &bootstrap.Client{}
+//	b2.Cache = cache.NewDiskCache()
 //
-//   dsr2 := b.DNS()  // Loads dns.json from disk cache.
+//	dsr2 := b.DNS()  // Loads dns.json from disk cache.
 //
 // This package also implements the experimental Service Provider registry. Due
 // to the experimental nature, no Service Registry file exists on data.iana.org
@@ -92,7 +94,7 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/url"
 	"time"
@@ -236,7 +238,7 @@ func (c *Client) download(ctx context.Context, registry RegistryType) ([]byte, R
 		return nil, nil, fmt.Errorf("Server returned non-200 status code: %s", resp.Status)
 	}
 
-	json, err := ioutil.ReadAll(resp.Body)
+	json, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -357,19 +359,18 @@ func (c *Client) Lookup(question *Question) (*Answer, error) {
 // This function never initiates a network transfer.
 func (c *Client) ASN() *ASNRegistry {
 	c.init()
-	c.freshenFromCache(ServiceProvider)
+	c.freshenFromCache(ASN)
 
 	s, _ := c.registries[ASN].(*ASNRegistry)
 	return s
 }
 
-//
 // DNS returns the current DNS Registry (or nil if the registry file hasn't been Download()ed).
 //
 // This function never initiates a network transfer.
 func (c *Client) DNS() *DNSRegistry {
 	c.init()
-	c.freshenFromCache(ServiceProvider)
+	c.freshenFromCache(DNS)
 
 	s, _ := c.registries[DNS].(*DNSRegistry)
 	return s
@@ -380,7 +381,7 @@ func (c *Client) DNS() *DNSRegistry {
 // This function never initiates a network transfer.
 func (c *Client) IPv4() *NetRegistry {
 	c.init()
-	c.freshenFromCache(ServiceProvider)
+	c.freshenFromCache(IPv4)
 
 	s, _ := c.registries[IPv4].(*NetRegistry)
 	return s
@@ -391,7 +392,7 @@ func (c *Client) IPv4() *NetRegistry {
 // This function never initiates a network transfer.
 func (c *Client) IPv6() *NetRegistry {
 	c.init()
-	c.freshenFromCache(ServiceProvider)
+	c.freshenFromCache(IPv6)
 
 	s, _ := c.registries[IPv6].(*NetRegistry)
 	return s
diff --git a/cli.go b/cli.go
index b874b97..5e86637 100644
--- a/cli.go
+++ b/cli.go
@@ -8,10 +8,10 @@ import (
 	"encoding/pem"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"net/url"
+	"os"
 	"strconv"
 	"strings"
 	"time"
@@ -421,7 +421,7 @@ func RunCLI(args []string, stdout io.Writer, stderr io.Writer, options CLIOption
 		if options.Sandbox {
 			p12, err = sandbox.LoadFile(p12FilenameAndPassword[0])
 		} else {
-			p12, err = ioutil.ReadFile(p12FilenameAndPassword[0])
+			p12, err = os.ReadFile(p12FilenameAndPassword[0])
 		}
 
 		// Check the file was read correctly.
diff --git a/client.go b/client.go
index 5b45cf3..daf498c 100644
--- a/client.go
+++ b/client.go
@@ -7,7 +7,7 @@ package rdap
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strings"
 	"time"
@@ -275,7 +275,7 @@ func (c *Client) get(rdapReq *Request) *HTTPResponse {
 	}
 
 	defer resp.Body.Close()
-	httpResponse.Body, httpResponse.Error = ioutil.ReadAll(resp.Body)
+	httpResponse.Body, httpResponse.Error = io.ReadAll(resp.Body)
 
 	httpResponse.Duration = time.Since(start)
 
diff --git a/sandbox/file.go b/sandbox/file.go
index 086ddc3..4b1e16d 100644
--- a/sandbox/file.go
+++ b/sandbox/file.go
@@ -6,8 +6,8 @@ package sandbox
 
 import (
 	"errors"
-	"io/ioutil"
 	"log"
+	"os"
 	"path"
 	"runtime"
 )
@@ -25,7 +25,7 @@ func LoadFile(filename string) ([]byte, error) {
 		sandboxPath = findPackagePath()
 	}
 
-	body, err := ioutil.ReadFile(path.Join(sandboxPath, filename))
+	body, err := os.ReadFile(path.Join(sandboxPath, filename))
 
 	if err != nil {
 		log.Panic(err)
diff --git a/test/file.go b/test/file.go
index 5244488..79cff47 100644
--- a/test/file.go
+++ b/test/file.go
@@ -5,8 +5,8 @@
 package test
 
 import (
-	"io/ioutil"
 	"log"
+	"os"
 	"path"
 	"runtime"
 )
@@ -20,7 +20,7 @@ func LoadFile(filename string) []byte {
 		testDataPath = findTestDataPath()
 	}
 
-	body, err := ioutil.ReadFile(path.Join(testDataPath, filename))
+	body, err := os.ReadFile(path.Join(testDataPath, filename))
 
 	if err != nil {
 		log.Panic(err)
@@ -39,4 +39,3 @@ func findTestDataPath() string {
 
 	return path.Join(dir, "testdata")
 }
-
diff --git a/test/http.go b/test/http.go
index c8ca93b..76d46d7 100644
--- a/test/http.go
+++ b/test/http.go
@@ -5,7 +5,7 @@
 package test
 
 import (
-	"io/ioutil"
+	"io"
 	"log"
 	"net/http"
 
@@ -59,7 +59,7 @@ func Get(url string) []byte {
 		log.Panic(err)
 	}
 
-	data, err := ioutil.ReadAll(resp.Body)
+	data, err := io.ReadAll(resp.Body)
 	defer resp.Body.Close()
 
 	if err != nil {