How to use libproxy in Vala

all: sample

sample: sample.vala
    valac --pkg libproxy-1.0 sample.vala

clean:
    rm sample

using px;

void main() {
  var pf = new px.ProxyFactory();
  string[] proxies = pf.get_proxies("https://github.com/libproxy/libproxy");

  foreach (string proxy in proxies) {
    stdout.printf ("%s\n", proxy);
  }
}