Replace ioutil with io

`ioutil` is deprecated, and on all the versions of Go we support, its
functionality is replaced with `io`.

Author: richvdh

fclient/client.go

@@ -21,7 +21,7 @@ import (
 	"crypto/tls"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net"
 	"net/http"
 	"net/url"
@@ -350,7 +350,7 @@ func (fc *Client) LookupUserInfo(
 	}
 	if response.StatusCode < 200 || response.StatusCode >= 300 {
 		var errorOutput []byte
-		errorOutput, err = ioutil.ReadAll(response.Body)
+		errorOutput, err = io.ReadAll(response.Body)
 		if err != nil {
 			return
 		}
@@ -525,7 +525,7 @@ func (fc *Client) DoRequestAndParseResponse(
 	if response.StatusCode/100 != 2 { // not 2xx
 		// Adapted from https://github.com/matrix-org/gomatrix/blob/master/client.go
 		var contents []byte
-		contents, err = ioutil.ReadAll(response.Body)
+		contents, err = io.ReadAll(response.Body)
 		if err != nil {
 			return err
 		}

fclient/federationclient_test.go

@@ -5,7 +5,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"reflect"
 	"strings"
@@ -63,7 +63,7 @@ func TestSendJoinFallback(t *testing.T) {
 					if strings.HasPrefix(req.URL.Path, "/_matrix/federation/v2/send_join") {
 						return &http.Response{
 							StatusCode: 404,
-							Body:       ioutil.NopCloser(strings.NewReader("404 not found")),
+							Body:       io.NopCloser(strings.NewReader("404 not found")),
 						}, nil
 					}
 					if !strings.HasPrefix(req.URL.Path, "/_matrix/federation/v1/send_join") {
@@ -72,7 +72,7 @@ func TestSendJoinFallback(t *testing.T) {
 					t.Logf("Sending response: %s", string(v1ResBytes))
 					return &http.Response{
 						StatusCode: 200,
-						Body:       ioutil.NopCloser(bytes.NewReader(v1ResBytes)),
+						Body:       io.NopCloser(bytes.NewReader(v1ResBytes)),
 					}, nil
 				},
 			},
@@ -126,12 +126,12 @@ func TestSendJoinJSON(t *testing.T) {
 						t.Logf("Sending response: %s", string(respSendJoinResponseJSON))
 						return &http.Response{
 							StatusCode: 200,
-							Body:       ioutil.NopCloser(bytes.NewReader(respSendJoinResponseJSON)),
+							Body:       io.NopCloser(bytes.NewReader(respSendJoinResponseJSON)),
 						}, nil
 					}
 					return &http.Response{
 						StatusCode: 404,
-						Body:       ioutil.NopCloser(strings.NewReader("404 not found")),
+						Body:       io.NopCloser(strings.NewReader("404 not found")),
 					}, nil
 				},
 			},
@@ -185,12 +185,12 @@ func TestSendTransactionToRelay(t *testing.T) {
 					if strings.HasPrefix(req.URL.Path, "/_matrix/federation/v1/send_relay") {
 						return &http.Response{
 							StatusCode: 200,
-							Body:       ioutil.NopCloser(bytes.NewReader(respSendResponseJSON)),
+							Body:       io.NopCloser(bytes.NewReader(respSendResponseJSON)),
 						}, nil
 					}
 					return &http.Response{
 						StatusCode: 404,
-						Body:       ioutil.NopCloser(strings.NewReader("404 not found")),
+						Body:       io.NopCloser(strings.NewReader("404 not found")),
 					}, nil
 				},
 			},
@@ -232,12 +232,12 @@ func TestSendTransactionToRelayReportsFailure(t *testing.T) {
 					if strings.HasPrefix(req.URL.Path, "/_matrix/federation/v1/send_relay") {
 						return &http.Response{
 							StatusCode: 400,
-							Body:       ioutil.NopCloser(bytes.NewReader(respSendResponseJSON)),
+							Body:       io.NopCloser(bytes.NewReader(respSendResponseJSON)),
 						}, nil
 					}
 					return &http.Response{
 						StatusCode: 404,
-						Body:       ioutil.NopCloser(strings.NewReader("404 not found")),
+						Body:       io.NopCloser(strings.NewReader("404 not found")),
 					}, nil
 				},
 			},

fclient/request.go

@@ -5,7 +5,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"mime"
 	"net/http"
 	"strings"
@@ -274,7 +273,7 @@ func readHTTPRequest(req *http.Request) (*FederationRequest, error) { // nolint:
 	result.fields.Method = req.Method
 	result.fields.RequestURI = req.URL.RequestURI()
 
-	content, err := ioutil.ReadAll(req.Body)
+	content, err := io.ReadAll(req.Body)
 	if err != nil {
 		return nil, err
 	}