Minor cleanups for staticcheck issues

staticcheck found a couple of minor code cleanup improvements, like
unused variables or an out-of-order defer, mostly in tests.

This patch fixes those problems by making the necessary adjustments.

They're all fairly small, and should not change the logic in any
significant way.

internal/dkim/dns_test.go

@@ -3,8 +3,6 @@ package dkim
 import (
 	"context"
 	"crypto"
-	"crypto/ed25519"
-	"crypto/x509"
 	"encoding/base64"
 	"errors"
 	"testing"
@@ -36,7 +34,6 @@ const exampleRSAKeyB64 = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQ" +
 	"tdY9tf6mcwGjaNBcWToIMmPSPDdQPNUYckcQ2QIDAQAB"
 
 var exampleRSAKeyBuf, _ = base64.StdEncoding.DecodeString(exampleRSAKeyB64)
-var exampleRSAKey, _ = x509.ParsePKCS1PublicKey(exampleRSAKeyBuf)
 
 // Ed25519 key from the RFC example.
 // https://datatracker.ietf.org/doc/html/rfc8463#appendix-A.2
@@ -44,7 +41,6 @@ const exampleEd25519KeyB64 = "11qYAYKxCrfVS/7TyWQHOg7hcvPapiMlrwIaaPcHURo="
 
 var exampleEd25519KeyBuf, _ = base64.StdEncoding.DecodeString(
 	exampleEd25519KeyB64)
-var exampleEd25519Key = ed25519.PublicKey(exampleEd25519KeyBuf)
 
 var results = map[string][]string{}
 var resultErr = map[string]error{}

internal/localrpc/e2e_test.go

@@ -22,10 +22,10 @@ func Hola(tr *trace.Trace, input url.Values) (url.Values, error) {
 	return output, nil
 }
 
-var testErr = errors.New("test error")
+var errTest = errors.New("test error")
 
 func HolaErr(tr *trace.Trace, input url.Values) (url.Values, error) {
-	return nil, testErr
+	return nil, errTest
 }
 
 type testServer struct {
@@ -86,7 +86,7 @@ func TestEndToEnd(t *testing.T) {
 		{"Echo", nil, mkV(), nil},
 		{"Echo", mkV("msg", "hola"), mkV("msg", "hola"), nil},
 		{"Hola", mkV("name", "marola"), mkV("greeting", "Hola marola"), nil},
-		{"HolaErr", nil, nil, testErr},
+		{"HolaErr", nil, nil, errTest},
 		{"UnknownMethod", nil, nil, errUnknownMethod},
 	}
 

internal/smtpsrv/conn.go

@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"context"
 	"crypto/tls"
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -944,7 +945,7 @@ func (c *Conn) runPostDataHook(data []byte) ([]byte, bool, error) {
 
 		// The error contains the last line of stdout, so filters can pass
 		// some rejection information back to the sender.
-		err = fmt.Errorf(lastLine(string(out)))
+		err = errors.New(lastLine(string(out)))
 		return nil, permanent, err
 	}
 

internal/smtpsrv/server.go

@@ -282,7 +282,6 @@ func (s *Server) periodicallyReload() {
 		return
 	}
 
-	//lint:ignore SA1015 This lasts the program's lifetime.
 	for range time.Tick(*reloadEvery) {
 		s.Reload()
 	}

test/util/smtpc/smtpc.go

@@ -56,11 +56,11 @@ func main() {
 		}
 
 		conn, err = tls.Dial("tcp", *addr, tlsConfig)
-		defer conn.Close()
 	} else {
 		conn, err = net.Dial("tcp", *addr)
 	}
 	notnil(err)
+	defer conn.Close()
 
 	// Send the message.
 	client, err := smtp.NewClient(conn, *addr)