gRPC Async implementation for prometheus

[chennupushkar]

We are converting our prometheus gRPC synchronous implementation to asynchronous implementation by changing grpc.ServerInterceptor to grpc.aio.ServerInterceptor. But this switch does not seem to be very easy. After making the switch to aio, we are not able to start the prometheus http server.

[chennupushkar]

I have added the implementation code and the error which i am seeing at https://stackoverflow.com/questions/64192211/how-to-convert-grpc-serverinterceptor-to-grcp-aio-serverinterceptor