Register transaction condition with each read Var only

1 files changed, 8 insertions, 4 deletions

diff --git a/var.go b/var.go
index 3494352..05e86cf 100644
--- a/var.go
+++ b/var.go
@@ -4,12 +4,16 @@ import "sync"
 
 // A Var holds an STM variable.
 type Var struct {
-	val     interface{}
-	version uint64
-	mu      sync.Mutex
+	val      interface{}
+	version  uint64
+	mu       sync.Mutex
+	watchers map[*Tx]struct{}
 }
 
 // NewVar returns a new STM variable.
 func NewVar(val interface{}) *Var {
-	return &Var{val: val}
+	return &Var{
+		val:      val,
+		watchers: make(map[*Tx]struct{}),
+	}
 }