Asynchronous code just means that the language 💬 has a way to tell the computer / program 🤖 that at some point in the code, it 🤖 will have to wait for *something else* to finish somewhere else. Let's say that *something else* is called "slow-file" 📝.

So, during that time, the computer can go and do some other work, while "slow-file" 📝 finishes.

At that point, by noticing that the server took some microseconds longer to send the "Incorrect username or password" response, the attackers will know that they got _something_ right, some of the initial letters were right.

And then they can try again knowing that it's probably something more similar to `stanleyjobsox` than to `johndoe`.

#### A "professional" attack

# JSON Compatible Encoder

There are some cases where you might need to convert a data type (like a Pydantic model) to something compatible with JSON (like a `dict`, `list`, etc).

For example, if you need to store it in a database.

For that, **FastAPI** provides a `jsonable_encoder()` function.

## Using the `jsonable_encoder`

Let's imagine that you have a database `fake_db` that only receives JSON compatible data.

    sourceCompatibility(JavaVersion.VERSION_11)
  }

  kotlinOptions {
    jvmTarget = JavaVersion.VERSION_11.toString()
  }

  // issue merging due to conflict with httpclient and something else
  packagingOptions.resources.excludes += setOf(
    "META-INF/DEPENDENCIES"
  )
}


dependencies {
  val okhttpLegacyVersion = "3.12.12"

  implementation(libs.kotlin.reflect)

The same as with SQLAlchemy, we are not doing something like:

```Python
user = await models.User.select().first()
```

...but instead we are using:

```Python
user = models.User.select().first()
```

So, again, we should declare the *path operation functions* and the dependency without `async def`, just with a normal `def`, as:

```Python hl_lines="2"
# Something goes here

しかし、依存関係を定義する方法はそれだけではありません（その方が一般的かもしれませんが）。

重要なのは、依存関係が「呼び出し可能」なものであることです。

Pythonにおける「**呼び出し可能**」とは、Pythonが関数のように「呼び出す」ことができるものを指します。

そのため、`something`オブジェクト（関数ではないかもしれませんが）を持っていて、それを次のように「呼び出す」（実行する）ことができるとします:

```Python
something()
```

または

```Python
something(some_argument, some_keyword_argument="foo")
```

これを「呼び出し可能」なものと呼びます。

## 依存関係としてのクラス

Pythonのクラスのインスタンスを作成する際に、同じ構文を使用していることに気づくかもしれません。

* 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**.

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

    val handshake = makeRequest(client)

    assertThat(handshake.cipherSuite).isIn(*expectedModernTls12CipherSuites.toTypedArray())

    // Probably something like
    // TLS_AES_128_GCM_SHA256
    // TLS_AES_256_GCM_SHA384
    // TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
    // TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
    // TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384

!!! 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.