example set proxy in spalsh lua script

splash_proxy.lua

function main(splash)
  local url = splash.args.url
  splash:set_user_agent("Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36")
  local host = 'host'
    local port = port
    local user = nil
    local password = nil
    splash:on_request(function (request)
        request:set_proxy{host, port, username=user, password=password}
    end)
    splash:go(splash.args.url)
  assert(splash:wait(5))
  return {
    html = splash:html(),
    png = splash:png(),
    har = splash:har(),
  }
end