code: func (file *GridFile) Abort() {
  	if file.mode != gfsWriting {
  		panic("file.Abort must be called on file opened for writing")
  	}
  	file.err = errors.New("write aborted")
  }
docs: // Abort cancels an in-progress write, preventing the file from being
  // automically created and ensuring previously written chunks are
  // removed when the file is closed.
  //
  // It is a runtime error to call Abort when the file was not opened
  // for writing.