code: async function saveToken (url, token) {
    let tokens
    try {
      const data = await readFile(credentialsPath)
      tokens = JSON.parse(data)
    } catch (err) {}
  
    // if it was empty or contained `null` for some reason
    if (typeof tokens !== 'object' || !tokens) {
      tokens = {}
    }
  
    tokens[url] = token
  
    await writeFile(credentialsPath, JSON.stringify(tokens, null, 2))
  }
docs: Store the JWT for an Upload Server URL in the credentials file.