fn chain<R>(self, next: R) -> Chain<Self, R>
    where
        Self: Sized,
        R: AsyncRead,
    {
        assert_read(Chain::new(self, next))
    }
Creates an adaptor which will chain this stream with another.

The returned `AsyncRead` instance will first read all bytes from this object
until EOF is encountered. Afterwards the output is equivalent to the
output of `next`.

# Examples

```
# futures::executor::block_on(async {
use futures::io::{AsyncReadExt, Cursor};

let reader1 = Cursor::new([1, 2, 3, 4]);
let reader2 = Cursor::new([5, 6, 7, 8]);

let mut reader = reader1.chain(reader2);
let mut buffer = Vec::new();

// read the value into a Vec.
reader.read_to_end(&mut buffer).await?;
assert_eq!(buffer, [1, 2, 3, 4, 5, 6, 7, 8]);
# Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap();
```
futures-util/src/io/mod.rs