code: func (pcond *ProxyConds) Do(h RespHandler) {
  	pcond.proxy.respHandlers = append(pcond.proxy.respHandlers,
  		FuncRespHandler(func(resp *http.Response, ctx *ProxyCtx) *http.Response {
  			for _, cond := range pcond.reqConds {
  				if !cond.HandleReq(ctx.Req, ctx) {
  					return resp
  				}
  			}
  			for _, cond := range pcond.respCond {
  				if !cond.HandleResp(resp, ctx) {
  					return resp
  				}
  			}
  			return h.Handle(resp, ctx)
  		}))
  }
docs: // ProxyConds.Do will register the RespHandler on the proxy, h.Handle(resp,ctx) will be called on every
  // request that matches the conditions aggregated in pcond.