hystrix pkg don't support fallback func

[wwangbo]

What would you like?

I want to use hystrix as cb and want to set fallback func once execute failed

[peterbourgon]

You can do this without explicit support in Go kit, can't you?

[wwangbo]

Yes, I can, but since our Go-Kit supports this function, we'd better support fallback in this function. Let me mention MR, is it ok for you?

[peterbourgon]

Feel free to make a PR but consider it a method of explanation, as I don't yet understand why this is important.