code: func (ds *dockerService) ExecSync(_ context.Context, req *runtimeapi.ExecSyncRequest) (*runtimeapi.ExecSyncResponse, error) {
  	timeout := time.Duration(req.Timeout) * time.Second
  	var stdoutBuffer, stderrBuffer bytes.Buffer
  	err := ds.streamingRuntime.exec(req.ContainerId, req.Cmd,
  		nil, // in
  		ioutils.WriteCloserWrapper(&stdoutBuffer),
  		ioutils.WriteCloserWrapper(&stderrBuffer),
  		false, // tty
  		nil,   // resize
  		timeout)
  
  	var exitCode int32
  	if err != nil {
  		exitError, ok := err.(utilexec.ExitError)
  		if !ok {
  			return nil, err
  		}
  
  		exitCode = int32(exitError.ExitStatus())
  	}
  	return &runtimeapi.ExecSyncResponse{
  		Stdout:   stdoutBuffer.Bytes(),
  		Stderr:   stderrBuffer.Bytes(),
  		ExitCode: exitCode,
  	}, nil
  }
docs: // ExecSync executes a command in the container, and returns the stdout output.
  // If command exits with a non-zero exit code, an error is returned.