pub fn new(message: T) -> Self {
        Request {
            metadata: MetadataMap::new(),
            message,
            extensions: Extensions::new(),
        }
    }
Create a new gRPC request.

```rust
# use tonic::Request;
# pub struct HelloRequest {
#   pub name: String,
# }
Request::new(HelloRequest {
name: "Bob".into(),
});
```
tonic/src/request.rs