Async RPC with callback over HTTP

I am in the process of designing an SDK (in Golang) with blocking functionality, which should be run asynchronously with the result being returned via a callback.

I have been playing with the Gorilla Toolkit RPC library which is great but I don't see a way of returning values of async calls.

Perhaps I am missing something and the RPC model does not support async calls, by that I mean all calls are blocking, even for a long time. If that is the case, i'm assuming there is no HTTP timeout then?

How can I implement async RPC calls with a return value being returned via a callback.

For clarification: I cannot use the typical Go Channel method for callbacks as I will be calling the RPC from another language over HTTP. So my question is, is there a way to implement callbacks over HTTP when doing RPC or should the calls just block, even for a long time until a value is ready to be returned?

I don't know about Gorilla, but in the net/rpc package of the standard library of Go you'll find this method net/rpc/Go. It makes a RPC call asynchronously, you give it a channel as parameter so you can retrieve the RPC reply when the Remote Procedure Call is finished.

net/rpc/Call also makes a RPC call but it is blocking until the call is finished. If you know how to use channels I'm sure you'll get what you want with the Go method.

You might take a look at grpc. This:

• Has a native go implementation

• Has a implementations for "Java, Python, etc" for most values of 'etc'

• Works over HTTP2 (OK, not quite http, but pretty similar)

• Is fully asynchronous (example happens to be C++).