code: func (s *Session) Setenv(name, value string) error {
  	msg := setenvRequest{
  		Name:  name,
  		Value: value,
  	}
  	ok, err := s.ch.SendRequest("env", true, Marshal(&msg))
  	if err == nil && !ok {
  		err = errors.New("ssh: setenv failed")
  	}
  	return err
  }
docs: // Setenv sets an environment variable that will be applied to any
  // command executed by Shell or Run.