code: func (s *Session) CombinedOutput(cmd string) ([]byte, error) {
  	if s.Stdout != nil {
  		return nil, errors.New("ssh: Stdout already set")
  	}
  	if s.Stderr != nil {
  		return nil, errors.New("ssh: Stderr already set")
  	}
  	var b singleWriter
  	s.Stdout = &b
  	s.Stderr = &b
  	err := s.Run(cmd)
  	return b.b.Bytes(), err
  }
docs: // CombinedOutput runs cmd on the remote host and returns its combined
  // standard output and standard error.