fix linter errors

.golangci.yml

@@ -16,3 +16,8 @@ run:
   build-tags:
   - test
   - e2e
+linters-settings:
+  revive:
+    rules:
+      - name: dot-imports
+        disabled: true

cmd/root.go

@@ -2,7 +2,6 @@ package cmd
 
 import (
 	"bytes"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -152,7 +151,7 @@ func checkIssuances(dc config.DomainConfig, c api.CertspotterClient, mailSender
 }
 
 func atomicWritePosition(pc config.PositionConfig) error {
-	tmpFile, err := ioutil.TempFile(filepath.Dir(pc.Filename), "position.*.toml")
+	tmpFile, err := os.CreateTemp(filepath.Dir(pc.Filename), "position.*.toml")
 	if err != nil {
 		return err
 	}
@@ -184,7 +183,7 @@ func getMailSenderForDomain(conf *config.Config, dc config.DomainConfig, default
 	return domainMailer
 }
 
-func runRoot(cmd *cobra.Command, args []string) error {
+func runRoot(_ *cobra.Command, _ []string) error {
 	_ = log.Info("ct-monitor", map[string]interface{}{
 		"version":  version,
 		"commit":   commit,

filter/common.go

@@ -54,6 +54,6 @@ func (p *IssuanceFilterPlugin) Server(*plugin.MuxBroker) (interface{}, error) {
 	return &IssuanceFilterRPCServer{Impl: p.Impl}, nil
 }
 
-func (*IssuanceFilterPlugin) Client(b *plugin.MuxBroker, c *rpc.Client) (interface{}, error) {
+func (*IssuanceFilterPlugin) Client(_ *plugin.MuxBroker, c *rpc.Client) (interface{}, error) {
 	return &IssuanceFilterRPCClient{client: c}, nil
 }

mailer/sendgrid.go

@@ -29,7 +29,9 @@ func (s *SendgridMailer) init() {
 }
 
 // Init implements the Mailer's Init interface.
-func (s SendgridMailer) Init(from, to string) error {
+func (s *SendgridMailer) Init(from, to string) error {
+	s.From = from
+	s.To = to
 	if s.From == "" {
 		return ErrMissingSender
 	}