Upgrade the linter and fix all new linter warnings

Also fix some tests that were broken by bumping golang and dependencies
in the previous commits.

Note that in addition to changes made to satisfy the linter which do not
impact the behavior of the code, this commit also adds ReadHeaderTimeout
to all usages of http.Server to satisfy the linter (and because it
seemed like a good suggestion).

test/testlib/cli.go

@@ -1,10 +1,9 @@
-// Copyright 2020-2021 the Pinniped contributors. All Rights Reserved.
+// Copyright 2020-2022 the Pinniped contributors. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
 package testlib
 
 import (
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -17,7 +16,7 @@ import (
 	"go.pinniped.dev/internal/testutil"
 )
 
-//nolint: gochecknoglobals
+//nolint:gochecknoglobals
 var pinnipedCLIBinaryCache struct {
 	buf   []byte
 	mutex sync.Mutex
@@ -38,7 +37,7 @@ func PinnipedCLIPath(t *testing.T) string {
 	path := filepath.Join(testutil.TempDir(t), "pinniped")
 	if pinnipedCLIBinaryCache.buf != nil {
 		t.Log("using previously built pinniped CLI binary")
-		require.NoError(t, ioutil.WriteFile(path, pinnipedCLIBinaryCache.buf, 0500))
+		require.NoError(t, os.WriteFile(path, pinnipedCLIBinaryCache.buf, 0500))
 		return path
 	}
 
@@ -49,7 +48,7 @@ func PinnipedCLIPath(t *testing.T) string {
 	t.Logf("built CLI binary in %s", time.Since(start).Round(time.Millisecond))
 
 	// Fill our cache so we don't have to do this again.
-	pinnipedCLIBinaryCache.buf, err = ioutil.ReadFile(path)
+	pinnipedCLIBinaryCache.buf, err = os.ReadFile(path)
 	require.NoError(t, err, string(output))
 
 	return path