VCL snippet that contains the minimum amount of config to support ESI using Surrogate headers

varnishv4esi.vcl

vcl 4.0;

backend default {
  .host = "127.0.0.1";
  .port = "8080";
}

sub vcl_recv {
  set req.http.Surrogate-Capability = "key=ESI/1.0";
}

sub vcl_backend_response {
    if (beresp.http.Surrogate-Control ~ "ESI/1.0") {
    unset beresp.http.Surrogate-Control;
    set beresp.do_esi = true;
  }
}