Pode ser muito útil para configurar **recursos** que você precisa usar por toda aplicação, e que são **compartilhados** entre as requisições, e/ou que você precisa **limpar** depois. Por exemplo, o pool de uma conexão com o banco de dados ou carregamento de um modelo compartilhado de aprendizado de máquina (_machine learning_).

## Caso de uso

Vamos iniciar com um exemplo de **caso de uso** e então ver como resolvê-lo com isso.

This can be very useful for setting up **resources** that you need to use for the whole app, and that are **shared** among requests, and/or that you need to **clean up** afterwards. For example, a database connection pool, or loading a shared machine learning model.

## Use Case

Let's start with an example **use case** and then see how to solve it with this.

	errInvalidKeypath         = errors.New("A provided keypath is invalid")
)

// qProp contains analysis info about an SQL term.
type qProp struct {
	isAggregation, isRowFunc bool

	err error
}

// `combine` combines a pair of `qProp`s, so that errors are
// propagated correctly, and checks that an aggregation is not being
// combined with a row-function term.

/// info

Da es sich um einen WebSocket handelt, macht es keinen Sinn, eine `HTTPException` auszulösen, stattdessen lösen wir eine `WebSocketException` aus.

Sie können einen „Closing“-Code verwenden, aus den <a href="https://tools.ietf.org/html/rfc6455#section-7.4.1" class="external-link" target="_blank">gültigen Codes, die in der Spezifikation definiert sind</a>.

///

### WebSockets mit Abhängigkeiten ausprobieren

   * <p><b>Performance note:</b> When feasible, {@code initialCapacity} should be the exact number
   * of values that will be added, if that knowledge is readily available. It is better to guess a
   * value slightly too high than slightly too low. If the value is not exact, the {@link
   * ImmutableIntArray} that is built will very likely occupy more memory than strictly necessary;
   * to trim memory usage, build using {@code builder.build().trimmed()}.

                            "name": "item_id",
                            "in": "path",
                        }
                    ],
                }
            },
            "/path/bool/{item_id}": {
                "get": {
                    "responses": {
                        "200": {
                            "description": "Successful Response",

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):

from typing import Optional

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):

        withLibraryDependencies<DependencyRemovalByNameRule>(libs.samplesCheck, setOf("slf4j-simple"))

        // asciidoctorj depends on a lot of stuff, which causes `Can't create process, argument list too long` on Windows
        withLibraryDependencies<DependencyRemovalByNameRule>("org.gradle:sample-discovery", setOf("asciidoctorj", "asciidoctorj-api"))

        withModule<DowngradeXmlApisRule>("jaxen:jaxen")

                            <h3 class="card-title">
                                <la:message key="labels.dict_kuromoji_list_link"/>
                            </h3>
                            <div class="card-tools">
                                <div class="btn-group">
                                    <la:link href="/admin/dict" styleClass="btn btn-default btn-xs">
                                        <em class="fa fa-book">