text: export default function TelegrafSession (opts) {
    const options = {
      property: 'session',
      store: new Map(),
      getSessionKey: (ctx) => ctx.from && ctx.chat && `${ctx.from.id}:${ctx.chat.id}`,
      ...opts
    }
  
    const ttlMs = options.ttl && options.ttl * 1000
  
    return (ctx, next) => {
      const key = options.getSessionKey(ctx)
      if (!key) {
        return next(ctx)
      }
      const now = new Date().getTime()
      return Promise.resolve(options.store.get(key))
        .then((state) => state || { session: {} })
        .then(({ session, expires }) => {
          if (expires && expires < now) {
            session = {}
          }
          Object.defineProperty(ctx, options.property, {
            get: function () { return session },
            set: function (newValue) { session = { ...newValue } }
          })
          return next(ctx).then(() => options.store.set(key, {
            session,
            expires: ttlMs ? now + ttlMs : null
          }))
        })
    }
  }
  