all: Don't let Suture capture panics (fixes #4758) (#5119)

Fork with new option.

lib/discover/cache.go

@@ -10,10 +10,10 @@ import (
 	stdsync "sync"
 	"time"
 
+	"github.com/calmh/suture"
 	"github.com/syncthing/syncthing/lib/protocol"
 	"github.com/syncthing/syncthing/lib/sync"
 	"github.com/syncthing/syncthing/lib/util"
-	"github.com/thejerf/suture"
 )
 
 // The CachingMux aggregates results from multiple Finders. Each Finder has
@@ -51,8 +51,10 @@ type cachedError interface {
 
 func NewCachingMux() CachingMux {
 	return &cachingMux{
-		Supervisor: suture.NewSimple("discover.cachingMux"),
-		mut:        sync.NewRWMutex(),
+		Supervisor: suture.New("discover.cachingMux", suture.Spec{
+			PanicPanics: true,
+		}),
+		mut: sync.NewRWMutex(),
 	}
 }