code: func DisableEcho(fd uintptr, state *State) error {
  	newState := state.termios
  	newState.Lflag &^= unix.ECHO
  
  	if err := tcset(fd, &newState); err != 0 {
  		return err
  	}
  	handleInterrupt(fd, state)
  	return nil
  }
docs: // DisableEcho applies the specified state to the terminal connected to the file
  // descriptor, with echo disabled.