Revert "Remove unuse import"

This reverts commit bfa7d3cf41.

src/machine/mod.rs

@@ -60,6 +60,7 @@ use std::sync::atomic::AtomicBool;
 
 use self::config::MachineConfig;
 use self::parsed_results::*;
+use tokio::runtime::Runtime;
 use rand::rngs::StdRng;
 use rand::SeedableRng;