From 974fed55d3ddd1b7d1e8a2e2e0d4daddcb57749a Mon Sep 17 00:00:00 2001
From: djmil <andriy@djmil.dev>
Date: Thu, 23 Apr 2026 20:02:34 +0000
Subject: [PATCH] happy path perf optimization
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move goroutineID() inside the defer, guarded by !finished. It's safe — Goexit runs defers in the same goroutine, so the ID is stable.
---
 pkg/result/result.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pkg/result/result.go b/pkg/result/result.go
index 4f2ddb2..edf677a 100644
--- a/pkg/result/result.go
+++ b/pkg/result/result.go
@@ -151,7 +151,6 @@ func Async[T any](fn func() T) <-chan Expect[T] {
 			val      T
 			finished bool
 		)
-		id := goroutineID()
 		defer func() {
 			if v := recover(); v != nil {
 				if err, ok := v.(*stackError); ok {
@@ -165,7 +164,8 @@ func Async[T any](fn func() T) <-chan Expect[T] {
 				ch <- Ok(val)
 				return
 			}
-			if stored, ok := gErrors.LoadAndDelete(id); ok {
+			// goroutineID is looked up here, on the error path only.
+			if stored, ok := gErrors.LoadAndDelete(goroutineID()); ok {
 				ch <- Fail[T](stored.(error))
 			} else {
 				ch <- Fail[T](errors.New("goroutine exited unexpectedly"))