add callback to subscribe

src/error/mod.rs

@@ -24,6 +24,19 @@ use solana_client::{
 };
 use solana_sdk::pubkey::ParsePubkeyError;
 
+#[derive(Debug)]
+#[allow(dead_code)]
+pub struct AppError(anyhow::Error);
+
+impl<E> From<E> for AppError
+where
+    E: Into<anyhow::Error>,
+{
+    fn from(err: E) -> Self {
+        Self(err.into())
+    }
+}
+
 #[derive(Debug)]
 pub enum ClientError {
     /// Bonding curve account was not found