code: func (pcond *ReqProxyConds) Do(h ReqHandler) {
  	pcond.proxy.reqHandlers = append(pcond.proxy.reqHandlers,
  		FuncReqHandler(func(r *http.Request, ctx *ProxyCtx) (*http.Request, *http.Response) {
  			for _, cond := range pcond.reqConds {
  				if !cond.HandleReq(r, ctx) {
  					return r, nil
  				}
  			}
  			return h.Handle(r, ctx)
  		}))
  }
docs: // ReqProxyConds.Do will register the ReqHandler on the proxy,
  // the ReqHandler will handle the HTTP request if all the conditions
  // aggregated in the ReqProxyConds are met. Typical usage:
  //	proxy.OnRequest().Do(handler) // will call handler.Handle(req,ctx) on every request to the proxy
  //	proxy.OnRequest(cond1,cond2).Do(handler)
  //	// given request to the proxy, will test if cond1.HandleReq(req,ctx) && cond2.HandleReq(req,ctx) are true
  //	// if they are, will call handler.Handle(req,ctx)