feat: add graceful shutdown with OS signal handling

Handle SIGINT/SIGTERM in Start() to cleanly drain all contexts,
stop goroutines, close SSE connections, and tear down PubSub.

Fix stopAllRoutines() to close() the channel instead of sending a
single value, so all listening goroutines are notified.

context.go

@@ -32,6 +32,7 @@ type Context struct {
 	reqCtx            context.Context
 	subscriptions     []Subscription
 	subsMu            sync.Mutex
+	disposeOnce       sync.Once
 }
 
 // View defines the UI rendered by this context.
@@ -350,11 +351,23 @@ func (c *Context) ReplaceURLf(format string, a ...any) {
 	c.ReplaceURL(fmt.Sprintf(format, a...))
 }
 
-// stopAllRoutines stops all go routines tied to this Context preventing goroutine leaks.
+// dispose idempotently tears down this context: unsubscribes all pubsub
+// subscriptions and closes ctxDisposedChan to stop routines and exit the SSE loop.
+func (c *Context) dispose() {
+	c.disposeOnce.Do(func() {
+		c.unsubscribeAll()
+		c.stopAllRoutines()
+	})
+}
+
+// stopAllRoutines closes ctxDisposedChan, broadcasting to all listening
+// goroutines (OnIntervalRoutine, SSE loop) that this context is done.
 func (c *Context) stopAllRoutines() {
 	select {
-	case c.ctxDisposedChan <- struct{}{}:
+	case <-c.ctxDisposedChan:
+		// already closed
 	default:
+		close(c.ctxDisposedChan)
 	}
 }
 

via.go

@@ -7,6 +7,7 @@
 package via
 
 import (
+	"context"
 	"crypto/rand"
 	_ "embed"
 	"encoding/hex"
@@ -16,9 +17,12 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	ossignal "os/signal"
 	"path/filepath"
 	"strings"
 	"sync"
+	"syscall"
+	"time"
 
 	"github.com/alexedwards/scs/v2"
 	"github.com/rs/zerolog"
@@ -34,6 +38,7 @@ var datastarJS []byte
 type V struct {
 	cfg                       Options
 	mux                       *http.ServeMux
+	server                    *http.Server
 	logger                    zerolog.Logger
 	contextRegistry           map[string]*Context
 	contextRegistryMutex      sync.RWMutex
@@ -254,14 +259,82 @@ func (v *V) getCtx(id string) (*Context, error) {
 	return nil, fmt.Errorf("ctx '%s' not found", id)
 }
 
-// Start starts the Via HTTP server on the given address.
+// Start starts the Via HTTP server and blocks until a SIGINT or SIGTERM
+// signal is received, then performs a graceful shutdown.
 func (v *V) Start() {
-	v.logInfo(nil, "via started at [%s]", v.cfg.ServerAddress)
 	handler := http.Handler(v.mux)
 	if v.sessionManager != nil {
 		handler = v.sessionManager.LoadAndSave(v.mux)
 	}
-	v.logger.Fatal().Err(http.ListenAndServe(v.cfg.ServerAddress, handler)).Msg("http server failed")
+	v.server = &http.Server{
+		Addr:    v.cfg.ServerAddress,
+		Handler: handler,
+	}
+
+	errCh := make(chan error, 1)
+	go func() {
+		errCh <- v.server.ListenAndServe()
+	}()
+
+	v.logInfo(nil, "via started at [%s]", v.cfg.ServerAddress)
+
+	sigCh := make(chan os.Signal, 1)
+	ossignal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
+
+	select {
+	case sig := <-sigCh:
+		v.logInfo(nil, "received signal %v, shutting down", sig)
+	case err := <-errCh:
+		if err != nil && err != http.ErrServerClosed {
+			v.logger.Fatal().Err(err).Msg("http server failed")
+		}
+		return
+	}
+
+	v.shutdown()
+}
+
+// Shutdown gracefully shuts down the server and all contexts.
+// Safe for programmatic or test use.
+func (v *V) Shutdown() {
+	v.shutdown()
+}
+
+func (v *V) shutdown() {
+	v.logInfo(nil, "draining all contexts")
+	v.drainAllContexts()
+
+	if v.server != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if err := v.server.Shutdown(ctx); err != nil {
+			v.logErr(nil, "http server shutdown error: %v", err)
+		}
+	}
+
+	if v.pubsub != nil {
+		if err := v.pubsub.Close(); err != nil {
+			v.logErr(nil, "pubsub close error: %v", err)
+		}
+	}
+
+	v.logInfo(nil, "shutdown complete")
+}
+
+func (v *V) drainAllContexts() {
+	v.contextRegistryMutex.Lock()
+	contexts := make([]*Context, 0, len(v.contextRegistry))
+	for _, c := range v.contextRegistry {
+		contexts = append(contexts, c)
+	}
+	v.contextRegistry = make(map[string]*Context)
+	v.contextRegistryMutex.Unlock()
+
+	for _, c := range contexts {
+		v.logDebug(c, "disposing context")
+		c.dispose()
+	}
+	v.logInfo(nil, "drained %d context(s)", len(contexts))
 }
 
 // HTTPServeMux returns the underlying HTTP request multiplexer to enable user extentions, middleware and
@@ -445,10 +518,10 @@ func New() *V {
 			case <-sse.Context().Done():
 				v.logDebug(c, "SSE connection ended")
 				return
-			case patch, ok := <-c.patchChan:
-				if !ok {
-					continue
-				}
+			case <-c.ctxDisposedChan:
+				v.logDebug(c, "context disposed, closing SSE")
+				return
+			case patch := <-c.patchChan:
 				switch patch.typ {
 				case patchTypeElements:
 					if err := sse.PatchElements(patch.content); err != nil {
@@ -530,8 +603,7 @@ func New() *V {
 			v.logErr(c, "failed to handle session close: %v", err)
 			return
 		}
-		c.unsubscribeAll()
-		c.stopAllRoutines()
+		c.dispose()
 		v.logDebug(c, "session close event triggered")
 		if v.cfg.DevMode {
 			v.devModeRemovePersisted(c)