timeout on singleton deadlock, closes #10

scope.go

@@ -1,8 +1,10 @@
 package dingo
 
 import (
+	"fmt"
 	"reflect"
 	"sync"
+	"time"
 )
 
 type (
@@ -56,7 +58,24 @@ func (s *SingletonScope) ResolveType(t reflect.Type, annotation string, unscoped
 	if l, ok := s.instanceLock[ident]; ok {
 		// we have the instance lock
 		s.mu.Unlock()
+
+		ticker := time.NewTimer(10 * time.Second)
+		go func() {
+			<-ticker.C
+			path := t.PkgPath()
+			if path == "" {
+				if t.Kind() == reflect.Ptr {
+					path = t.Elem().PkgPath()
+				}
+			}
+			if path != "" {
+				path += "."
+			}
+			path += t.Name()
+			panic(fmt.Sprintf("Singleton: timed out waiting for instance lock: type: %q,  annotation: %q", path, annotation))
+		}()
 		l.RLock()
+		ticker.Stop()
 		defer l.RUnlock()
 
 		instance, _ := s.instances.Load(ident)

scope_test.go

@@ -148,3 +148,23 @@ func TestInheritedScope(t *testing.T) {
 	secondI := i.(*inheritedScopeInjected)
 	assert.Same(t, firstI.i, secondI.i)
 }
+
+type circSingletonA struct {
+	B *circSingletonB `inject:""`
+}
+type circSingletonB struct {
+	A *circSingletonA `inject:""`
+}
+
+func TestCircularSingletonBinding(t *testing.T) {
+	EnableCircularTracing()
+	defer func() {
+		traceCircular = nil
+	}()
+	injector, err := NewInjector()
+	assert.NoError(t, err)
+	injector.Bind(new(circSingletonA)).In(Singleton)
+	assert.Panics(t, func() {
+		injector.GetInstance(new(circSingletonA))
+	})
+}