cmd/cli: improving loop guard test

We see number of failed test in Github Action, mostly on MacOS or
Windows due to the fact that goroutines are scheduled to be run
consequently.

This commit improves the test, ensuring at least 2 goroutines were
started before increasing the counting.

cmd/cli/loop_test.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"sync"
+	"sync/atomic"
 	"testing"
 )
 
@@ -9,16 +10,19 @@ func Test_loopGuard(t *testing.T) {
 	lg := newLoopGuard()
 	key := "foo"
 
-	var mu sync.Mutex
-	i := 0
+	var i atomic.Int64
+	var started atomic.Int64
 	n := 1000
 	do := func() {
 		locked := lg.TryLock(key)
 		defer lg.Unlock(key)
+		started.Add(1)
+		for started.Load() < 2 {
+			// Wait until at least 2 goroutines started, otherwise, on system with heavy load,
+			// or having only 1 CPU, all goroutines can be scheduled to run consequently.
+		}
 		if locked {
-			mu.Lock()
-			i++
-			mu.Unlock()
+			i.Add(1)
 		}
 	}
 
@@ -32,7 +36,7 @@ func Test_loopGuard(t *testing.T) {
 	}
 	wg.Wait()
 
-	if i == n {
+	if i.Load() == int64(n) {
 		t.Fatalf("i must not be increased %d times", n)
 	}
 }