How to host Flutter Webapp on a subfolder?

Question

I'm trying to host a webApp inside a subfolder of my host. I uploaded all the contents of the build/web folder, but in the console I get the error:

how can i set url of my subfolder?

{
"name": "pagamento",
"short_name": "pagamento",
"start_url": "./pagamenti",
"display": "standalone",
"background_color": "#0175C2",
"theme_color": "#0175C2",
"description": "A new Flutter project.",
"orientation": "portrait-primary",
"prefer_related_applications": false,
"icons": [
    {
        "src": "icons/Icon-192.png",
        "sizes": "192x192",
        "type": "image/png"
    },
    {
        "src": "icons/Icon-512.png",
        "sizes": "512x512",
        "type": "image/png"
    },
    {
        "src": "icons/Icon-maskable-192.png",
        "sizes": "192x192",
        "type": "image/png",
        "purpose": "maskable"
    },
    {
        "src": "icons/Icon-maskable-512.png",
        "sizes": "512x512",
        "type": "image/png",
        "purpose": "maskable"
    }
]

}

but it did not work

thank you and happy 2023 to all.