From 7bc2a0b786759c7320f6dbd9d32ce3c86e4cc8d8 Mon Sep 17 00:00:00 2001
From: qmuntal <qmuntaldiaz@microsoft.com>
Date: Mon, 24 Jul 2023 12:19:27 +0200
Subject: [PATCH] double checked locking

---
 statemachine.go | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/statemachine.go b/statemachine.go
index 7d6dcb2..be3631f 100644
--- a/statemachine.go
+++ b/statemachine.go
@@ -309,10 +309,13 @@ func (sm *StateMachine) stateRepresentation(state State) *stateRepresentation {
 	sr, ok := sm.stateConfig[state]
 	sm.stateMutex.RUnlock()
 	if !ok {
-		sr = newstateRepresentation(state)
 		sm.stateMutex.Lock()
-		sm.stateConfig[state] = sr
-		sm.stateMutex.Unlock()
+		defer sm.stateMutex.Unlock()
+		// Check again, since another goroutine may have added it while we were waiting for the lock.
+		if sr, ok = sm.stateConfig[state]; !ok {
+			sr = newstateRepresentation(state)
+			sm.stateConfig[state] = sr
+		}
 	}
 	return sr
 }