Replace assert.Fail with assert.FailNow (#27578)

assert.Fail() will continue to execute the code while assert.FailNow()
not. I thought those uses of assert.Fail() should exit immediately.
PS: perhaps it's a good idea to use
[require](https://pkg.go.dev/github.com/stretchr/testify/require)
somewhere because the assert package's default behavior does not exit
when an error occurs, which makes it difficult to find the root error
reason.

modules/process/manager_test.go

@@ -50,7 +50,7 @@ func TestManager_Cancel(t *testing.T) {
 	select {
 	case <-ctx.Done():
 	default:
-		assert.Fail(t, "Cancel should cancel the provided context")
+		assert.FailNow(t, "Cancel should cancel the provided context")
 	}
 	finished()
 
@@ -62,7 +62,7 @@ func TestManager_Cancel(t *testing.T) {
 	select {
 	case <-ctx.Done():
 	default:
-		assert.Fail(t, "Cancel should cancel the provided context")
+		assert.FailNow(t, "Cancel should cancel the provided context")
 	}
 	finished()
 }