You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: fields.go
    path of file: ./repos/hubble-ui/backend/vendor/k8s.io/kube-openapi/pkg/internal/third_party/go-json-experiment/json
    
    the code of the file until where you have to start completion: // Copyright 2021 The Go Authors. All rights reserved.
/
    
func consumeTagOption(in string) (string, int, error) {
	switch r, _ := utf8.DecodeRuneInString(in); {
	// Option as a Go identifier.
	case r == '_' || unicode.IsLetter(r):
		n := len(in) - len(strings.TrimLeftFunc(in, isLetterOrDigit))
		return in[:n], n, nil
	// Option as a single-quoted string.
	case r == '\'':
		// The grammar is nearly identical to a double-quoted Go string literal,
		// but uses single quotes as the terminators. The reason for a custom
		// grammar is because both backtick and double quotes cannot be used
		// verbatim in a struct tag.
		//
		// Convert a single-quoted string to a double-quote string and rely on
		// strconv.Unquote to handle the rest.
		var inEscape bool
		b := []byte{'"'}
		n := len(`'`)
		for len(in) > n {
			r, rn := utf8.DecodeRuneInString(in[n:])
			switch {
			case inEscape:
				if r == '\'' {
					b = b[:len(b)-1] // remove escape character: `\'` => `'`
				}
				inEscape = false
			case r == '\\':
				inEscape = true
			case r == '"':
				b = append(b, '\\') // insert escape character: `"` => `\"`
			case r == '\'':
				b = append(b, '"')
				n += len(`'`)
				out, err := strconv.Unquote(string(b))
				if err != nil {
					return "", 0, fmt.Errorf("invalid single-quoted string: %s", in[:n])
				}
				return out, n, nil
			}
			b = append(b, in[n:][:rn]...)
			n += rn
		}
		if n > 10 {
			n = 10 // limit the amount of context printed in the error
		}
		return "", 0, fmt.Errorf("single-quoted string not terminated: %s...", in[:n])
	case len(in) == 0:
		return "", 0, io.ErrUnexpectedEOF
	default:
		return "", 0, fmt.Errorf("invalid character %q at start of option (expecting Unicode letter or single quote)", r)
	}
}