public BaseClient getClient(@Nonnull final String serviceName) {
        if (MapUtils.isEmpty(environments)) {
            throw new IllegalArgumentException("environments is empty");
        }
        BaseClient client = environments.get(serviceName);
        if (Objects.isNull(client)) {
            throw new IllegalArgumentException("service name not found: " + serviceName);
        }
        return client;
    }
get client.

@param serviceName serviceName
@return service client
shenyu-e2e/shenyu-e2e-client/src/main/java/org/apache/shenyu/e2e/client/EnvironmentClient.java