From f62b5fd7f27c067144236eb8722c89ee91a9b2c5 Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Fri, 27 Jun 2025 02:03:07 +0300
Subject: [PATCH] sync: add implementation for WaitGroup.go/1, add test
 (#24797)

---
 vlib/sync/waitgroup.c.v    | 11 +++++++++++
 vlib/sync/waitgroup_test.v | 13 +++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/vlib/sync/waitgroup.c.v b/vlib/sync/waitgroup.c.v
index 6ed3076164..507789cf65 100644
--- a/vlib/sync/waitgroup.c.v
+++ b/vlib/sync/waitgroup.c.v
@@ -82,3 +82,14 @@ pub fn (mut wg WaitGroup) wait() {
 	C.atomic_fetch_add_u32(voidptr(&wg.wait_count), 1)
 	wg.sem.wait() // blocks until task_count becomes 0
 }
+
+// go starts `f` in a new thread, arranging to call wg.add(1) before that,
+// and wg.done() in the same thread. The function `f` should not panic.
+// Calls to wg.go() should happen before the call to wg.wait().
+pub fn (mut wg WaitGroup) go(f fn ()) {
+	wg.add(1)
+	spawn fn (mut wg WaitGroup, f fn ()) {
+		f()
+		wg.done()
+	}(mut wg, f)
+}
diff --git a/vlib/sync/waitgroup_test.v b/vlib/sync/waitgroup_test.v
index cc473f5e57..6afed8cf3c 100644
--- a/vlib/sync/waitgroup_test.v
+++ b/vlib/sync/waitgroup_test.v
@@ -39,3 +39,16 @@ fn test_waitgroup_no_use() {
 	wg.wait()
 	done = true
 }
+
+fn test_waitgroup_go() {
+	mut counter := 0
+	p := unsafe { &counter }
+	mut wg := new_waitgroup()
+	for i in 0 .. 10 {
+		wg.go(fn [p] () {
+			unsafe { (*p)++ }
+		})
+	}
+	wg.wait()
+	assert counter == 10
+}