_ref is not defined

[bbhxwl]

vue2 ，

  methods: {
    async btnTest() {
      let getName = greenlet( async username => {
        let url = `https://api.github.com/users/${username}`
        let res = await fetch(url)
        let profile = await res.json()
        return profile.name
      })
      console.log(await getName('developit'))
    },
  },