public <S, Q> S postGateway(final String path, final Map<String, Object> headers, final Q req, final Class<S> respType) throws IOException {
        String respBody = post(path, headers, req);
        LOG.info("postGateway({}) resp({})", path, respBody);
        try {
            return GSON.fromJson(respBody, respType);
        } catch (Exception e) {
            return (S) respBody;
        }
    }
Send a post http request to shenyu gateway with header.

@param <S>      type of response object
@param <Q>      type of request object
@param path     path
@param headers  http header
@param req      request body as an object
@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