[koa-prometheus] Error: Unknown meter type: undefined

```js
const Meter = require('@uswitch/koa-prometheus').default

const meters = Meter({ /* Config */ }, { loadDefaults: true })

```

```
xxx/node_modules/@uswitch/koa-prometheus/build/utils/build-meters.js:48
[1]   if (!Meter) throw new Error('Unknown meter type: ' + type);
[1]               ^
[1] 
[1] Error: Unknown meter type: undefined
```