p5.js parent() | Uncaught (in promise) TypeError: Cannot read properties of null (reading ‘appendChild’)

I do exactly as the library docs here.

I have an error

Uncaught (in promise) TypeError: Cannot read properties of null (reading 'appendChild')

index.html

<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" href="styles/index.css" />
        <script src="libs/p5.min.js"></script>
        <script src="scripts/barcode.js"></script>
    </head>
    <body>
        <div class="container"></div>
    </body>
</html>

Tried defer on the barcode script import, and putting it in the end.

barcode.js

function setup() {
    let cnv = createCanvas(500, 500);
    cnv.parent("container");
}

Tried this, nothing changed

async function setup() {
        let cnv = await createCanvas(500, 500);
        cnv.parent("container");
}

Thanks for your insight !