hapijs 17 server.method async issue

example.js

const Hapi = require('hapi')

const double = (input) => {
    return new Promise(resolve => {
        setTimeout(() => {
            return resolve(input+input)
        }, 500)
    })
}

const initServer = async() => {
    const server = new Hapi.Server({
        port: 4001
    })

    server.method('double', double, {
        cache: {
            generateTimeout: 100,
            expiresIn: 60*1000
        }
    })

    server.route({
        path: '/double/{input}',
        method: 'GET',
        async handler(request, h) {
            return await request.server.methods.double(request.params.input)
        } 
    })

    await server.start()
    console.log(`server started at ${server.info.uri}`)
}

initServer()

/*
first request for http://localhost:4001/double/test                                                                                                                                        -- INSERT --
{"statusCode":503,"error":"Service Unavailable","message":"Service Unavailable"}

sequential calls (with the same parameter) return
testtest
*/