code: func (req *Request) SetBodyStreamWriter(sw StreamWriter) {
  	sr := NewStreamReader(sw)
  	req.SetBodyStream(sr, -1)
  }
docs: // SetBodyStreamWriter registers the given sw for populating request body.
  //
  // This function may be used in the following cases:
  //
  //     * if request body is too big (more than 10MB).
  //     * if request body is streamed from slow external sources.
  //     * if request body must be streamed to the server in chunks
  //     (aka `http client push` or `chunked transfer-encoding`).
  //
  // Note that GET and HEAD requests cannot have body.
  //
  /// See also SetBodyStream.