shlex.go
func NewLexer(r io.Reader, posix, whitespacesplit bool) *Lexer {
	return &Lexer{
		reader:          bufio.NewReader(r),
		tokenizer:       &DefaultTokenizer{},
		posix:           posix,
		whitespacesplit: whitespacesplit,
	}
}
func NewLexer(r io.Reader, posix, whitespacesplit bool) *Lexer {
	return &Lexer{
		reader:          bufio.NewReader(r),
		tokenizer:       &DefaultTokenizer{},
		posix:           posix,
		whitespacesplit: whitespacesplit,
	}
}
// NewLexer creates a new Lexer reading from io.Reader.  This Lexer
// has a DefaultTokenizer according to posix and whitespacesplit
// rules.