git » spf » commit 7a83916

diff --git a/cmd/spf-check/spf-check.go b/cmd/spf-check/spf-check.go
index 86c3d1e..2ac4d16 100644
--- a/cmd/spf-check/spf-check.go
+++ b/cmd/spf-check/spf-check.go
@@ -37,7 +37,7 @@ func main() {
 
 	opts := []spf.Option{}
 	if *debug {
-		traceF := func(f string, a ...interface{}) {
+		traceF := func(f string, a ...any) {
 			fmt.Printf("debug: "+f+"\n", a...)
 		}
 		opts = append(opts, spf.WithTraceFunc(traceF))
diff --git a/spf.go b/spf.go
index 3de4bf3..bc73e36 100644
--- a/spf.go
+++ b/spf.go
@@ -23,6 +23,7 @@ import (
 	"net"
 	"net/url"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 )
@@ -32,7 +33,7 @@ import (
 type Result string
 
 // Valid results.
-var (
+const (
 	// https://tools.ietf.org/html/rfc7208#section-8.1
 	// Not able to reach any conclusion.
 	None = Result("none")
@@ -114,10 +115,10 @@ const (
 )
 
 // TraceFunc is the type of tracing functions.
-type TraceFunc func(f string, a ...interface{})
+type TraceFunc func(f string, a ...any)
 
 var (
-	nullTrace    = func(f string, a ...interface{}) {}
+	nullTrace    = func(f string, a ...any) {}
 	defaultTrace = nullTrace
 )
 
@@ -147,7 +148,7 @@ func CheckHost(ip net.IP, domain string) (Result, error) {
 		maxvoidcount: defaultMaxVoidLookups,
 		helo:         domain,
 		sender:       "@" + domain,
-		ctx:          context.TODO(),
+		ctx:          context.Background(),
 		resolver:     defaultResolver,
 		trace:        defaultTrace,
 	}
@@ -195,7 +196,7 @@ func CheckHostWithSender(ip net.IP, helo, sender string, opts ...Option) (Result
 		maxvoidcount: defaultMaxVoidLookups,
 		helo:         helo,
 		sender:       sender,
-		ctx:          context.TODO(),
+		ctx:          context.Background(),
 		resolver:     defaultResolver,
 		trace:        defaultTrace,
 	}
@@ -481,13 +482,14 @@ func (r *resolution) getDNSRecord(domain string) (string, error) {
 	// 1 record is what we expect, return the record.
 	// More than that, it's a permanent error:
 	// https://tools.ietf.org/html/rfc7208#section-4.5
-	l := len(records)
-	if l == 0 {
+	switch len(records) {
+	case 0:
 		return "", nil
-	} else if l == 1 {
+	case 1:
 		return records[0], nil
+	default:
+		return "", ErrMultipleRecords
 	}
-	return "", ErrMultipleRecords
 }
 
 func isTemporary(err error) bool {
@@ -937,19 +939,19 @@ func (r *resolution) expandMacros(s, domain string) (string, error) {
 	macroS := ""
 
 	var err error
-	n := ""
+	var n strings.Builder
 	for _, c := range s {
 		if afterPercent {
 			afterPercent = false
 			switch c {
 			case '%':
-				n += "%"
+				n.WriteString("%")
 				continue
 			case '_':
-				n += " "
+				n.WriteString(" ")
 				continue
 			case '-':
-				n += "%20"
+				n.WriteString("%20")
 				continue
 			case '{':
 				inMacroDefinition = true
@@ -1033,14 +1035,12 @@ func (r *resolution) expandMacros(s, domain string) (string, error) {
 
 			// Reverse if requested.
 			if reverse {
-				reverseStrings(split)
+				slices.Reverse(split)
 			}
 
 			// Leave the last $digits fields, if given.
 			if digits > 0 {
-				if digits > len(split) {
-					digits = len(split)
-				}
+				digits = min(digits, len(split))
 				split = split[len(split)-digits:]
 			}
 
@@ -1054,24 +1054,18 @@ func (r *resolution) expandMacros(s, domain string) (string, error) {
 				str = url.QueryEscape(str)
 			}
 
-			n += str
+			n.WriteString(str)
 			continue
 		}
 		if c == '%' {
 			afterPercent = true
 			continue
 		}
-		n += string(c)
+		n.WriteString(string(c))
 	}
 
-	r.trace("macro expanded %q to %q", s, n)
-	return n, nil
-}
-
-func reverseStrings(a []string) {
-	for left, right := 0, len(a)-1; left < right; left, right = left+1, right-1 {
-		a[left], a[right] = a[right], a[left]
-	}
+	r.trace("macro expanded %q to %q", s, n.String())
+	return n.String(), nil
 }
 
 func ipToMacroStr(ip net.IP) string {
diff --git a/spf_test.go b/spf_test.go
index 8aa5cae..5ba1623 100644
--- a/spf_test.go
+++ b/spf_test.go
@@ -801,7 +801,7 @@ func TestBadResolverResponse(t *testing.T) {
 
 func TestWithTraceFunc(t *testing.T) {
 	calls := 0
-	var trace TraceFunc = func(f string, a ...interface{}) {
+	var trace TraceFunc = func(f string, a ...any) {
 		calls++
 		t.Logf("tracing "+f, a...)
 	}
diff --git a/yml_test.go b/yml_test.go
index e9f94f2..181e6ce 100644
--- a/yml_test.go
+++ b/yml_test.go
@@ -6,6 +6,7 @@ import (
 	"io"
 	"net"
 	"os"
+	"slices"
 	"strings"
 	"testing"
 
@@ -124,7 +125,7 @@ type MX struct {
 }
 
 func (mx *MX) UnmarshalYAML(value *yaml.Node) error {
-	seq := []interface{}{}
+	seq := []any{}
 	if err := value.Decode(&seq); err != nil {
 		return err
 	}
@@ -266,12 +267,7 @@ func testRFC(t *testing.T, fname string) {
 }
 
 func resultIn(got Result, exp []string) bool {
-	for _, e := range exp {
-		if e == string(got) {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(exp, string(got))
 }
 
 // Take a reverse-dns host name of the form:
@@ -288,7 +284,7 @@ func reverseDNS(t *testing.T, r string) net.IP {
 
 		// Break down in pieces, and construct the ipv4 string backwards.
 		pieces := strings.Split(r, ".")
-		for i := 0; i < len(pieces); i++ {
+		for i := range pieces {
 			s += pieces[len(pieces)-1-i] + "."
 		}
 		s = s[:len(s)-1]
@@ -298,7 +294,7 @@ func reverseDNS(t *testing.T, r string) net.IP {
 
 		// Break down in pieces, and construct the ipv6 string backwards.
 		pieces := strings.Split(r, ".")
-		for i := 0; i < len(pieces); i++ {
+		for i := range pieces {
 			s += pieces[len(pieces)-1-i]
 			if i%4 == 3 {
 				s += ":"