In general, ASGI middlewares are classes that expect to receive an ASGI app as the first argument.

So, in the documentation for third-party ASGI middlewares they will probably tell you to do something like:

```Python
from unicorn import UnicornMiddleware

app = SomeASGIApp()

new_app = UnicornMiddleware(app, some_config="rainbow")
```

/// info | "`@decorator` Info"

That `@something` syntax in Python is called a "decorator".

You put it on top of a function. Like a pretty decorative hat (I guess that's where the term came from).

A "decorator" takes the function below and does something with it.

The server handler function has this signature: `type SingleHandlerFn func(payload []byte) ([]byte, *RemoteErr)`.

Sample handler:
```go
    handler :=  func(payload []byte) ([]byte, *grid.RemoteErr) {
        // Do something with payload
        return []byte("response"), nil
    }

    err := manager.RegisterSingleHandler(grid.HandlerDiskInfo, handler)
```

Sample call:
```go
    // Get a connection to the remote host

    return suite;
  }

  private static final String STRING = ASCII + I18N;
  private static final String LINES = "foo\nbar\r\nbaz\rsomething";
  private static final ImmutableList<String> SPLIT_LINES =
      ImmutableList.of("foo", "bar", "baz", "something");

  private TestCharSource source;

  @Override
  public void setUp() {
    source = new TestCharSource(STRING);
  }

    assertEquals(
        "text/plain; something=\"cr@zy\"; something-else=\"crazy with spaces\";"
            + " and-another-thing=\"\"; normal-thing=foo",
        MediaType.create("text", "plain")
            .withParameter("something", "cr@zy")
            .withParameter("something-else", "crazy with spaces")
            .withParameter("and-another-thing", "")

   * String.class}, then {@code new TypeResolver().where(formal, actual)} will {@linkplain
   * #resolveType resolve} {@code ParameterizedType List<T>} to {@code List<String>}, and resolve
   * {@code Map<T, Something>} to {@code Map<String, Something>} etc. Similarly, {@code formal} and
   * {@code actual} can be {@code Map<K, V>} and {@code Map<String, Integer>} respectively, or they

## Return Type and Data Filtering

Let's continue from the previous example. We wanted to **annotate the function with one type**, but we wanted to be able to return from the function something that actually includes **more data**.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.
* Then it passes the **request** to be processed by the rest of the application (by some *path operation*).
* It then takes the **response** generated by the application (by some *path operation*).
* It can do something to that **response** or run any needed code.
* Then it returns the **response**.

#
# Windows-specific utilities.
#

# Docker on Windows has difficulty using volumes other than C:\, when it comes
# to setting up up volume mappings.
# Thus, the drive letter is replaced with C:\, in case it's
# something else (ex. T:), which is frequently the case inside Kokoro jobs.
function replace_drive_letter_with_c () {
  sed -E "s|^[a-zA-Z]:|C:|g" <<< $1

We also saw that HTTPS is normally provided by a component **external** to your application server, a **TLS Termination Proxy**.

And there has to be something in charge of **renewing the HTTPS certificates**, it could be the same component or it could be something different.

### Example Tools for HTTPS

Some of the tools you could use as a TLS Termination Proxy are:

* Traefik