Upgrade to tokio 1.0

Cargo.toml

@@ -20,7 +20,7 @@ parking_lot = "0.11.0"
 rand = "0.7.3"
 serde = "1.0.116"
 serde_derive = "1.0.116"
-tokio = { version = "0.3", features = ["rt-multi-thread", "time", "parking_lot"] }
+tokio = { version = "1.0", features = ["rt-multi-thread", "time", "parking_lot"] }
 
 [dev-dependencies]
 anyhow = "1.0"