fix(toolkit): make use of tokio runtime

Author: aesedepece

Cargo.lock

@@ -14,3 +14,4 @@ serde_json = "1.0.66"
 structopt = "0.3.22"
 witnet_data_structures = { path = "../data_structures", default-features = false }
 witnet_rad = { path = "../rad", default-features = false }
+tokio = { version = "1.44.1", features = ["rt", "rt-multi-thread", "macros"] }

toolkit/Cargo.toml

@@ -28,7 +28,8 @@ mod cli;
 ///
 /// This basically handles the core functionality of the CLI, and ensures that the process exits
 /// gracefully.
-fn main() {
+#[tokio::main]
+async fn main() {
     let command = Command::from_args();
     let exit_code = cli::process_command(command);
     std::process::exit(exit_code);