pass variable from custom module file to twig template in d8
First create a function that returns the variable, something like this:

function my_function() {
return $var_name;
}


Then you must create a preprocess function, for the template, like this:

function MY_MODULE_preprocess_TEMPLATE(&amp;$variables) {
  $V_NAME = my_function();
  $variables['v-name'] = $V_NAME;
}


Remember to clear the cache.