Sumit

@extrawurst I know this is probably annoying. But can you give this another approval ? I have done a `make check` `make test` and `make build-release` so atleast the linux...

@extrawurst any input on this ?

[try 2] @extrawurst does this go in the right direction ?

Is this still relevant ( even after resolving the conflicts) ? @extrawurst

@googlebot I signed it

@bradfitz could you please have a look at this ? does this help in anyway ?

If the features is acceptable then if required I will add tests

I have added tests. but I dont understand why the callbacks are failing for `struct{}`

okay that should do it. Let me know what you think

Any reviews on this one ?