Couldn't load Header tool in toolbox

I'm using HTML template engine that comes with go-fiber. I think I've set the configuration properly and other tools like quotes have been shown on the toolbox. But the Header tool still isn't showing.
This is my config js:
```js
const editor = new EditorJS({
holder: 'editorjs',
autofocus: true,
tools: {
image: SimpleImage,
quote: Quote,
header: Header
},
data: {}
})
```

Here is my HTML:
```html

```