migrate away from deprecated ioutil APIs (#7175)

Co-authored-by: Callum Waters <cmwaters19@gmail.com>
Co-authored-by: M. J. Fromberger <fromberger@interchain.io>

rpc/jsonrpc/client/http_json_client.go

@@ -6,7 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net"
 	"net/http"
 	"net/url"
@@ -219,7 +219,7 @@ func (c *Client) Call(
 
 	defer httpResponse.Body.Close()
 
-	responseBytes, err := ioutil.ReadAll(httpResponse.Body)
+	responseBytes, err := io.ReadAll(httpResponse.Body)
 	if err != nil {
 		return nil, fmt.Errorf("failed to read response body: %w", err)
 	}
@@ -267,7 +267,7 @@ func (c *Client) sendBatch(ctx context.Context, requests []*jsonRPCBufferedReque
 
 	defer httpResponse.Body.Close()
 
-	responseBytes, err := ioutil.ReadAll(httpResponse.Body)
+	responseBytes, err := io.ReadAll(httpResponse.Body)
 	if err != nil {
 		return nil, fmt.Errorf("read response body: %w", err)
 	}

rpc/jsonrpc/client/http_json_client_test.go

@@ -1,7 +1,7 @@
 package client
 
 import (
-	"io/ioutil"
+	"io"
 	"log"
 	"net/http"
 	"net/http/httptest"
@@ -21,7 +21,7 @@ func TestHTTPClientMakeHTTPDialer(t *testing.T) {
 	defer tsTLS.Close()
 	// This silences a TLS handshake error, caused by the dialer just immediately
 	// disconnecting, which we can just ignore.
-	tsTLS.Config.ErrorLog = log.New(ioutil.Discard, "", 0)
+	tsTLS.Config.ErrorLog = log.New(io.Discard, "", 0)
 
 	for _, testURL := range []string{ts.URL, tsTLS.URL} {
 		u, err := newParsedURL(testURL)

rpc/jsonrpc/client/http_uri_client.go

@@ -3,7 +3,7 @@ package client
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strings"
 
@@ -76,7 +76,7 @@ func (c *URIClient) Call(ctx context.Context, method string,
 	}
 	defer resp.Body.Close()
 
-	responseBytes, err := ioutil.ReadAll(resp.Body)
+	responseBytes, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, fmt.Errorf("read response body: %w", err)
 	}