code: func NewClient(opts ClientOpts) *Client {
  	if opts.HTTPClient == nil {
  		opts.HTTPClient = &http.Client{}
  	}
  
  	return &Client{
  		token:      opts.Token,
  		baseURL:    opts.BaseURL,
  		httpClient: opts.HTTPClient,
  		userAgent:  opts.UserAgent,
  	}
  }
docs: // NewClient returns a client instance.