feat(transport): Allow custom IO and UDS example (#184)

Closes #136

examples/src/uds/client.rs

@@ -0,0 +1,39 @@
+#[cfg(unix)]
+
+pub mod hello_world {
+    tonic::include_proto!("helloworld");
+}
+
+use hello_world::{greeter_client::GreeterClient, HelloRequest};
+use http::Uri;
+use std::convert::TryFrom;
+use tokio::net::UnixStream;
+use tonic::transport::Endpoint;
+use tower::service_fn;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // We will ignore this uri because uds do not use it
+    // if your connector does use the uri it will be provided
+    // as the request to the `MakeConnection`.
+    let channel = Endpoint::try_from("lttp://[::]:50051")?
+        .connect_with_connector(service_fn(|_: Uri| {
+            let path = "/tmp/tonic/helloworld";
+
+            // Connect to a Uds socket
+            UnixStream::connect(path)
+        }))
+        .await?;
+
+    let mut client = GreeterClient::new(channel);
+
+    let request = tonic::Request::new(HelloRequest {
+        name: "Tonic".into(),
+    });
+
+    let response = client.say_hello(request).await?;
+
+    println!("RESPONSE={:?}", response);
+
+    Ok(())
+}