--- /dev/null
+/**
+ * Implements hook_block_build_alter().
+ */
+function {{ machine_name }}_block_build_alter(array &$build, \Drupal\Core\Block\BlockPluginInterface $block) {
+ // Add the 'user' cache context to some blocks.
+ if ($some_condition) {
+ $build['#cache']['contexts'][] = 'user';
+ }
+}