replace original session cookie

max_age.go

@@ -5,6 +5,9 @@ package traefik_session_max_age
 import (
 	"context"
 	"net/http"
+	"net/textproto"
+	"strconv"
+	"strings"
 )
 
 // Config the plugin configuration.
@@ -29,13 +32,30 @@ func (rww responseWriterWrapper) Header() http.Header {
 }
 
 func (rww responseWriterWrapper) WriteHeader(code int) {
-	if rww.cookieName != "" {
-		res := http.Response{Header: rww.ResponseWriter.Header()}
-		cookies := res.Cookies()
-		for _, cookie := range cookies {
-			if cookie.Name == rww.cookieName {
-				cookie.MaxAge = rww.maxAge
-				http.SetCookie(rww.ResponseWriter, cookie)
+	cookies := rww.ResponseWriter.Header()["Set-Cookie"]
+	if rww.cookieName != "" && len(cookies) > 0 {
+		for i, line := range cookies {
+			parts := strings.Split(textproto.TrimString(line), ";")
+			if len(parts) == 1 && parts[0] == "" {
+				continue
+			}
+			parts[0] = textproto.TrimString(parts[0])
+			name, _, ok := strings.Cut(parts[0], "=")
+			if !ok {
+				continue
+			}
+			buf := make([]byte, 0, 19)
+			name = textproto.TrimString(name)
+			if name == rww.cookieName {
+				var b strings.Builder
+				b.WriteString(line)
+				if rww.maxAge > 0 {
+					b.WriteString("; Max-Age=")
+					b.Write(strconv.AppendInt(buf, int64(rww.maxAge), 10))
+				} else if rww.maxAge < 0 {
+					b.WriteString("; Max-Age=0")
+				}
+				cookies[i] = b.String()
 			}
 		}
 	}