diff --git a/cmd/clientsim/main.go b/cmd/clientsim/main.go
index c546b9b..06c3f98 100644
--- a/cmd/clientsim/main.go
+++ b/cmd/clientsim/main.go
@@ -27,9 +27,10 @@ import (
 	"sync"
 	"time"
 
-	"git.cacert.org/cacert-gosigner/pkg/messages"
 	"github.com/justincpresley/go-cobs"
 	"github.com/shamaton/msgpackgen/msgpack"
+
+	"git.cacert.org/cacert-gosigner/pkg/messages"
 )
 
 const cobsDelimiter = 0x00
@@ -94,7 +95,7 @@ func (c *clientSimulator) handleInput(ctx context.Context) error {
 		default:
 			count, err := os.Stdin.Read(buf)
 			if err != nil {
-				return err
+				return fmt.Errorf("reading input failed: %w", err)
 			}
 
 			if count == 0 {
@@ -107,7 +108,7 @@ func (c *clientSimulator) handleInput(ctx context.Context) error {
 
 			err = cobs.Verify(data, cobsConfig)
 			if err != nil {
-				return err
+				return fmt.Errorf("frame verification failed: %w", err)
 			}
 
 			c.responses <- cobs.Decode(data, cobsConfig)
@@ -157,7 +158,7 @@ func (c *clientSimulator) Run() error {
 	var inputError, commandError error
 
 	go func(inputErr error) {
-		inputError = c.handleInput(ctx)
+		_ = c.handleInput(ctx)
 
 		cancel()
 
@@ -165,7 +166,7 @@ func (c *clientSimulator) Run() error {
 	}(inputError)
 
 	go func(commandErr error) {
-		commandErr = c.handleCommands(ctx)
+		_ = c.handleCommands(ctx)
 
 		cancel()
 
diff --git a/pkg/messages/resolver.msgpackgen.go b/pkg/messages/resolver.msgpackgen.go
index a999ce5..00240d5 100644
--- a/pkg/messages/resolver.msgpackgen.go
+++ b/pkg/messages/resolver.msgpackgen.go
@@ -4,6 +4,7 @@ package messages
 
 import (
 	"fmt"
+
 	msgpack "github.com/shamaton/msgpackgen/msgpack"
 	dec "github.com/shamaton/msgpackgen/msgpack/dec"
 	enc "github.com/shamaton/msgpackgen/msgpack/enc"
diff --git a/pkg/x509/helper/helper.go b/pkg/x509/helper/helper.go
index ace3a68..2578b2a 100644
--- a/pkg/x509/helper/helper.go
+++ b/pkg/x509/helper/helper.go
@@ -1,3 +1,20 @@
+/*
+Copyright 2022 CAcert Inc.
+SPDX-License-Identifier: Apache-2.0
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 package helper
 
 import (
@@ -9,7 +26,7 @@ import (
 // GenerateRandomSerial generates a random serial number to be used in X.509 certificates. The implementation is
 // compliant to https://www.rfc-editor.org/rfc/rfc5280#section-4.1.2.2.
 func GenerateRandomSerial() (*big.Int, error) {
-	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 160))
+	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 160)) //nolint:gomnd
 	if err != nil {
 		return nil, fmt.Errorf("could not generate random serial number: %w", err)
 	}
diff --git a/pkg/x509/helper/helper_test.go b/pkg/x509/helper/helper_test.go
index 662a8f3..2d5bcd0 100644
--- a/pkg/x509/helper/helper_test.go
+++ b/pkg/x509/helper/helper_test.go
@@ -1,10 +1,28 @@
+/*
+Copyright 2022 CAcert Inc.
+SPDX-License-Identifier: Apache-2.0
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 package helper_test
 
 import (
 	"testing"
 
-	"git.cacert.org/cacert-gosigner/pkg/x509/helper"
 	"github.com/stretchr/testify/assert"
+
+	"git.cacert.org/cacert-gosigner/pkg/x509/helper"
 )
 
 func TestGenerateRandomSerial(t *testing.T) {
diff --git a/pkg/x509/revoking/revoking_test.go b/pkg/x509/revoking/revoking_test.go
index bb8d934..8c05213 100644
--- a/pkg/x509/revoking/revoking_test.go
+++ b/pkg/x509/revoking/revoking_test.go
@@ -28,10 +28,11 @@ import (
 	"math/big"
 	"testing"
 
-	"git.cacert.org/cacert-gosigner/pkg/x509/helper"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"git.cacert.org/cacert-gosigner/pkg/x509/helper"
+
 	"git.cacert.org/cacert-gosigner/pkg/x509/revoking"
 )
 
diff --git a/pkg/x509/signing/signing_test.go b/pkg/x509/signing/signing_test.go
index 3fd186a..6435afb 100644
--- a/pkg/x509/signing/signing_test.go
+++ b/pkg/x509/signing/signing_test.go
@@ -28,9 +28,10 @@ import (
 	"testing"
 	"time"
 
-	"git.cacert.org/cacert-gosigner/pkg/x509/helper"
 	"github.com/stretchr/testify/assert"
 
+	"git.cacert.org/cacert-gosigner/pkg/x509/helper"
+
 	"git.cacert.org/cacert-gosigner/pkg/x509/signing"
 )