chore: remove futures dependency and update GcpSigner to use Tokio runtime for blocking execution

Author: incubator4

Cargo.lock

@@ -15,7 +15,6 @@ tracing = "0.1"
 tokio = { version = "1.0", features = ["full"] }
 pem = "3.0.4"
 hex = "0.4.3"
-futures = "0.3.31"
 
 [dev-dependencies]
 tokio = { version = "1.0", features = ["full"] }

Cargo.toml

@@ -1,6 +1,5 @@
 #![cfg_attr(debug_assertions, allow(dead_code, unused_imports))]
 use core::fmt;
-use futures::executor::block_on;
 use std::{cell::OnceCell, sync::Arc};
 
 use gcloud_sdk::{
@@ -152,7 +151,10 @@ impl Signer for GcpSigner {
         &self,
         message: &[u8],
     ) -> Result<solana_sdk::signature::Signature, SignerError> {
-        block_on(request_sign_data(&self.client, &self.key_name, message))
+        let rt = tokio::runtime::Runtime::new()
+            .map_err(|e| SignerError::Custom(format!("Failed to create tokio runtime: {:?}", e)))?;
+
+        rt.block_on(request_sign_data(&self.client, &self.key_name, message))
             .and_then(decode_signature)
             .map_err(Into::into)
     }