use rust tokio asyc gRPC to build rust cli wallet

[dckc]

Some libraries include:
...

• a gRPC client and server

https://tokio.rs/blog/2019-08-alphas/

[dckc]

Houston, we have liftoff!

~/projects/spendr$ cargo run
   Compiling spendr v0.1.0 (/home/connolly/projects/spendr)
    Finished dev [unoptimized + debuginfo] target(s) in 3.00s
     Running `target/debug/spendr`
RESPONSE = Response { metadata: MetadataMap { headers: {"content-type": "application/grpc", "grpc-encoding": "identity", "grpc-accept-encoding": "gzip"} }, message: Streaming }

now to check it in...

[dckc]

works in one case:
https://github.com/dckc/spendr 97e7fe7

[dckc]

doesn't look like the new async / await stuff has made it up to the gRPC level yet

tower-rs/tower-grpc#198