code: func DialHTTPWithClient(endpoint string, client *http.Client) (*Client, error) {
  	req, err := http.NewRequest(http.MethodPost, endpoint, nil)
  	if err != nil {
  		return nil, err
  	}
  	req.Header.Set("Content-Type", contentType)
  	req.Header.Set("Accept", contentType)
  
  	initctx := context.Background()
  	return newClient(initctx, func(context.Context) (ServerCodec, error) {
  		return &httpConn{client: client, req: req, closed: make(chan interface{})}, nil
  	})
  }
docs: // DialHTTPWithClient creates a new RPC client that connects to an RPC server over HTTP
  // using the provided HTTP Client.