Add lint

large futures

Cargo.toml

@@ -49,6 +49,7 @@ inefficient_to_string = "warn"
 items_after_statements = "warn"
 iter_not_returning_iterator = "warn"
 large_digit_groups = "warn"
+large_futures = "warn"
 large_stack_arrays = "warn"
 large_types_passed_by_value = "warn"
 lossy_float_literal = "warn"