How can I get a users from user public Twitter list by Twitter API

Question

My problem is with a "cursor" in Twitter API. I know how to get users from public Twitter list, but I've got only the first 20 user. As I read at Twitter API doc , there is a parameter "cursor". With cursor I gen get next chunk of data, but I'm completly stuck how to do it.

My script is:

# package checking

require(httr)
require(jsonlite)

# authorization

myapp = oauth_app("TT_APIR", key="xxxxxxx", secret="xxxxxxx")
sig=sign_oauth1.0(myapp, token="xxxxxxx",token_secret="xxxxxx")

# Get list members Twitter's list "official-twitter-accts"

listMembersGet= GET("https://api.twitter.com/1.1/lists/members.json?slug=official- twitter-accts&owner_screen_name=twitter", sig)
listMembersContent = content(listMembersGet)
listMembers=jsonlite::fromJSON(toJSON(listMembersContent))

# endo of script

Anyone can help?