code: func New(opt Opt) (*Builder, error) {
  	reqHandler := newReqBodyHandler(tracing.DefaultTransport)
  
  	c, err := newController(reqHandler, opt)
  	if err != nil {
  		return nil, err
  	}
  	b := &Builder{
  		controller:     c,
  		reqBodyHandler: reqHandler,
  		jobs:           map[string]*buildJob{},
  	}
  	return b, nil
  }
docs: // New creates a new builder