private <Q> String post(final String path, final Map<String, Object> headers, final Q req) throws IOException {
        Request.Builder requestBuilder = new Request.Builder().post(RequestBody.create(GSON.toJson(req), JSON)).url(gatewayEndpoint + path).addHeader(Constants.LOCAL_KEY, localKey);
        if (!CollectionUtils.isEmpty(headers)) {
            headers.forEach((key, value) -> requestBuilder.addHeader(key, String.valueOf(value)));
        }
        Response response = client.newCall(requestBuilder.build()).execute();
        return Objects.requireNonNull(response.body()).string();
    }
Send a post http request to shenyu gateway with custom requestBody.

@param <S>         type of response object
@param path        path
@param requestBody request Body
@param respType    response type passed to {@link Gson#fromJson(String, Class)}
@return response s
@throws IOException IO exception
shenyu-integrated-test/shenyu-integrated-test-common/src/main/java/org/apache/shenyu/integratedtest/common/helper/HttpHelper.java