Optional types

[ninedraft]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go1.8beta1

What operating system and processor architecture are you using (go env)?

windows/amd64
linux/amd64

What did you expect to see?

Something like

type RequestResult option{
   error
   Response 
}

and

type LoggerOptions option{
    JSON
    Text
    Protobuf
}

What did you see instead?

Pain, darkness and "const-iota" hell