FuncFilterInputRune fails on filtering ctrl-J

[isacikgoz]

Hi, when I implement the FuncFilterInputRune like below, it fails to filtering it. It places a rune, but blocks all input after.

func filterInput(r rune) (rune, bool) {
	switch r {
	// block CtrlJ feature
	case readline.CharCtrlJ:
		return 'a', true
	}
	return r, true
}

Can be reporoduced on demo: Just replace my implementation and see the result.

https://github.com/chzyer/readline/blob/2972be24d48e78746da79ba8e24e8b488c9880de/example/readline-demo/readline-demo.go#L64

My env is: darwin amd64, iterm2

Thanks in advance