Use atomic for shutdownAt

modules/caddyhttp/app.go

@@ -214,8 +214,6 @@ func (app *App) Provision(ctx caddy.Context) error {
 		srv.ctx = ctx
 		srv.logger = app.logger.Named("log")
 		srv.errorLogger = app.logger.Named("log.error")
-		srv.shutdownAtMu = new(sync.RWMutex)
-
 		if srv.Metrics != nil {
 			srv.logger.Warn("per-server 'metrics' is deprecated; use 'metrics' in the root 'http' app instead")
 			app.Metrics = cmp.Or(app.Metrics, &Metrics{
@@ -689,9 +687,7 @@ func (app *App) Stop() error {
 				for _, addr := range na.Expand() {
 					if caddy.ListenerUsage(addr.Network, addr.JoinHostPort(0)) < 2 {
 						app.logger.Debug("listener closing and shutdown delay is configured", zap.String("address", addr.String()))
-						server.shutdownAtMu.Lock()
-						server.shutdownAt = scheduledTime
-						server.shutdownAtMu.Unlock()
+						server.shutdownAt.Store(&scheduledTime)
 						delay = true
 					} else {
 						app.logger.Debug("shutdown delay configured but listener will remain open", zap.String("address", addr.String()))

modules/caddyhttp/replacer.go

@@ -387,17 +387,14 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 		switch key {
 		case "http.shutting_down":
 			server := req.Context().Value(ServerCtxKey).(*Server)
-			server.shutdownAtMu.RLock()
-			defer server.shutdownAtMu.RUnlock()
-			return !server.shutdownAt.IsZero(), true
+			return server.shutdownAt.Load() != nil, true
 		case "http.time_until_shutdown":
 			server := req.Context().Value(ServerCtxKey).(*Server)
-			server.shutdownAtMu.RLock()
-			defer server.shutdownAtMu.RUnlock()
-			if server.shutdownAt.IsZero() {
+			t := server.shutdownAt.Load()
+			if t == nil {
 				return nil, true
 			}
-			return time.Until(server.shutdownAt), true
+			return time.Until(*t), true
 		}
 
 		return nil, false

modules/caddyhttp/server.go

@@ -28,7 +28,7 @@ import (
 	"runtime"
 	"slices"
 	"strings"
-	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/caddyserver/certmagic"
@@ -291,8 +291,7 @@ type Server struct {
 
 	trustedProxies IPRangeSource
 
-	shutdownAt   time.Time
-	shutdownAtMu *sync.RWMutex
+	shutdownAt atomic.Pointer[time.Time]
 
 	// registered callback functions
 	connStateFuncs   []func(net.Conn, http.ConnState)