Add option to format output as json

src/main.rs

@@ -38,6 +38,9 @@ const DHCP_RELAY_AGENT_AND_SERVER_PORT: u16 = 547;
 struct Cli {
     /// Network interface name used for DHCPv6
     interface: String,
+    /// Format output as json
+    #[arg(long)]
+    json: bool,
 }
 
 #[derive(Serialize)]
@@ -154,9 +157,17 @@ async fn main() -> Result<()>{
     };
 
     let message_map = message_to_map(&response_msg);
-    let message_map_yaml = serde_yaml::to_string(&message_map)
-        .context("Unable to format message to yaml")?;
-    println!("{}", message_map_yaml);
+
+    if cli.json {
+        let message_map_json = serde_json::to_string(&message_map)
+            .context("Unable to format message to json")?;
+        println!("{}", message_map_json);
+    }
+    else {
+        let message_map_yaml = serde_yaml::to_string(&message_map)
+            .context("Unable to format message to yaml")?;
+        println!("{}", message_map_yaml);
+    }
 
     Ok(())
 }