examples: Fetch chianHead body

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

examples/examples/chainhead_subscription.rs

@@ -15,6 +15,8 @@ use subxt::{
     PolkadotConfig,
 };
 
+use futures::StreamExt;
+
 #[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata.scale")]
 pub mod polkadot {}
 
@@ -25,6 +27,15 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     // Create a client to use:
     let api = OnlineClient::<PolkadotConfig>::new().await?;
 
+    let mut follow_sub = api.blocks().subscribe_chainhead_finalized(false).await?;
+    // Handle all subscriptions from the `chainHead_follow`.
+    while let Some(event) = follow_sub.next().await {
+        let event = event?;
+
+        let body = event.body().await?;
+        println!("[hash={:?}] body={:?}", event.hash(), body);
+    }
+
     // Subscribe to the `chainHead_follow` method.
     let mut follow_sub = api.rpc().subscribe_chainhead_follow(false).await?;