func ParseJsonTag(tag string) (string, jsonTagOptions) {
	if idx := strings.Index(tag, ","); idx != -1 {
		return tag[:idx], jsonTagOptions(tag[idx+1:])
	}
	return tag, jsonTagOptions("")
}
parseTag splits a struct field's json tag into its name and
comma-separated options.
package utils
import (
	"strings"
)
type jsonTagOptions string