pkg/types: Avoid potential double lock of tsafeSet.

(tsafeSet).Sub and (tsafeSet).Equals can cause double lock bug if ts and other is pointing the same variable

gofmt the code and add some comments

pkg/types/set.go

@@ -148,6 +148,14 @@ func (ts *tsafeSet) Contains(value string) (exists bool) {
 func (ts *tsafeSet) Equals(other Set) bool {
 	ts.m.RLock()
 	defer ts.m.RUnlock()
+
+	// If ts and other represent the same variable, avoid calling
+	// ts.us.Equals(other), to avoid double RLock bug
+	if _other, ok := other.(*tsafeSet); ok {
+		if _other == ts {
+			return true
+		}
+	}
 	return ts.us.Equals(other)
 }
 
@@ -173,6 +181,15 @@ func (ts *tsafeSet) Copy() Set {
 func (ts *tsafeSet) Sub(other Set) Set {
 	ts.m.RLock()
 	defer ts.m.RUnlock()
+
+	// If ts and other represent the same variable, avoid calling
+	// ts.us.Sub(other), to avoid double RLock bug
+	if _other, ok := other.(*tsafeSet); ok {
+		if _other == ts {
+			usResult := NewUnsafeSet()
+			return &tsafeSet{usResult, sync.RWMutex{}}
+		}
+	}
 	usResult := ts.us.Sub(other).(*unsafeSet)
 	return &tsafeSet{usResult, sync.RWMutex{}}
 }