Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do? If possible, provide a recipe for reproducing the error.

	f := func(g func() error) {}
	f(func() error {
		failpoint.Inject("XXX", func() {
			failpoint.Return(errors.New("mock error"))
		})
		return nil
	})

2. What did you expect to see?
   After enabled failpoint,failpoint.Inject can be changed to failpoint.Eval.

3. What did you see instead?

Nothing changed

4. Versions of the failpoint

   • failpoint-ctl version (run failpoint-ctl -V):
     The version comes from tidb's go.mod

     v0.0.0-20200702092429-9f69995143ce