问为什么React钩子useRef在使用时会抛出错误？

EN

Compiled with problems:X

ERROR


src\components\SignIn.js
  Line 5:21:  React Hook "useRef" is called in function "signin" that is neither a React function component nor a custom React Hook function. React component names must start with an uppercase letter. React Hook names must start with the word "use"  react-hooks/rules-of-hooks

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import React, { useRef } from 'react'
import { Card, Button, Form } from 'react-bootstrap'

export default function signin() {
    const userRef = useRef()

    return (
        <>
            <Card>
                <Card.Body>
                    <h2 className='text-center mb-4'>Magnet</h2>
                    <Form>
                        <Form.Group id="username">
                            <Form.Label>Username</Form.Label>
                            <Form.Control type='text' ref={userRef} required />
                        </Form.Group>
                    </Form>
                </Card.Body>
            </Card>
        </>
    )
}