c = URI.open(u) {|res| res.meta["cache-control"] }
use http::header::CACHE_CONTROL;
let c = res.headers()
.get(CACHE_CONTROL)
.expect("cache-control header exists")
.to_str()
.expect("cache-control header contains only visible ascii");
let c = res.headers()
.get(CACHE_CONTROL)
.expect("cache-control header exists")
.to_str()
.expect("cache-control header contains only visible ascii");