Golang Regular Expression: Getting index position of variable

Question

I have a regular expression that has variables (?P<next_tok>) how can I grab the index of that variable match?

Here is the complete regexp: \S*[\.\?!](?P<after_tok>(?:[?!)";}\]\*:@\'\({\[])|\s+(?P<next_tok>\S+))

Example: http://play.golang.org/p/7CYfK50W2Q

I want to get the matches AND the index of any variable in the regexp match. Is this possible in golang?

EDIT: I couldn't figure out how to get next_tok by name, but I was able to get all the submatches via FindAllStringSubmatchIndex

http://play.golang.org/p/SEaCLVKisr