semaphore: avoid loop variable capture by closure

Change-Id: I21c5dc48ffe43aa27c50a42f9c9a01ac1f0c747c
Reviewed-on: https://go-review.googlesource.com/40991
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Glenn Lewis <gmlewis@google.com>

semaphore/semaphore_test.go

diff --git a/semaphore/semaphore_test.go b/semaphore/semaphore_test.go
index ad35dc2..867f71a 100644
--- a/semaphore/semaphore_test.go
+++ b/semaphore/semaphore_test.go
@@ -33,6 +33,7 @@
 	var wg sync.WaitGroup
 	wg.Add(n)
 	for i := 0; i < n; i++ {
+		i := i
 		go func() {
 			defer wg.Done()
 			HammerWeighted(sem, int64(i), 1000)