diff --git a/boomer.go b/boomer.go
index 5719069c..7d02078d 100644
--- a/boomer.go
+++ b/boomer.go
@@ -53,12 +53,13 @@ func (b *hrpBoomer) Run(testcases ...ITestCase) {
 
 func (b *hrpBoomer) convertBoomerTask(testcase *TestCase) *boomer.Task {
 	hrpRunner := NewRunner(nil).SetDebug(b.debug)
-	runner := hrpRunner.newCaseRunner(testcase)
 	config := testcase.Config.ToStruct()
 	return &boomer.Task{
 		Name:   config.Name,
 		Weight: config.Weight,
 		Fn: func() {
+			runner := hrpRunner.newCaseRunner(testcase)
+
 			testcaseSuccess := true       // flag whole testcase result
 			var transactionSuccess = true // flag current transaction result
 
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 26a81198..9b970960 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -1,6 +1,10 @@
 # Release History
 
-## v0.3.0 (2021-12-22)
+## v0.4.0 (2021-12-30)
+
+- fix: concurrent map writes in load testing
+
+## v0.3.0 (2021-12-24)
 
 - feat: implement `transaction` mechanism for load test
 - feat: continue running next step when failure occurs with `--continue-on-failure` flag, default to failfast