Most likely the reason this is hanging is because hook you are using is not complete. woocommerce_payment_complete_order_status is a hook for a filter but you are using an add_action. The hook for the add_action should be woocommerce_payment_complete_order_status_{$get_status}
resource for filter
http://hookr.io/plugins/woocommerce/3.0.6/filters/woocommerce_payment_complete_order_status/
apply_filters( 'woocommerce_payment_complete_order_status', 'create_fundraiser_purchase_post', 10, 2 );
resource for action
http://hookr.io/plugins/woocommerce/3.0.6/actions/woocommerce_payment_complete_order_status_get_status/
add_action( 'woocommerce_payment_complete_order_status_{$get_status}', 'create_fundraiser_purchase_post', 10, 2 );