code: func (t *BasicAuthTransport) RoundTrip(req *http.Request) (*http.Response, error) {
  	req2 := cloneRequest(req) // per RoundTripper contract
  
  	req2.SetBasicAuth(t.Username, t.Password)
  	return t.transport().RoundTrip(req2)
  }
docs: // RoundTrip implements the RoundTripper interface.  We just add the
  // basic auth and return the RoundTripper for this transport type.