Use AtomicU64 instead of `Mutex`

near-client/src/client.rs

 use serde_json::{json, Value};
 use url::Url;
 
-use std::sync::{Arc, Mutex};
-
-type AtomicNonce = Arc<Mutex<Nonce>>;
-
+use std::sync::{
+    atomic::{AtomicU64, Ordering},
+    Arc,
+};
 
+type AtomicNonce = Arc<AtomicU64>;
 /// Used for signing transactions
 pub struct Signer {
     keypair: Keypair,
         Ok(Self {
             keypair: Keypair::from_expanded_secret(secret_key).map_err(Error::CreateSigner)?,
             account_id,
-            nonce: AtomicNonce::new(Mutex::new(nonce)),
+            nonce: AtomicNonce::new(AtomicU64::new(nonce)),
         })
     }
 
         Self {
             keypair: Keypair::new(secret_key),
             account_id,
-            nonce: AtomicNonce::new(Mutex::new(nonce)),
+            nonce: AtomicNonce::new(AtomicU64::new(nonce)),
         }
     }
 
     }
 
     pub fn nonce(&self) -> Nonce {
-        *self.nonce.lock().unwrap()
+        self.nonce.load(Ordering::Acquire)
     }
 
     pub fn update_nonce(&self, nonce: Nonce) {
-        *self.nonce.lock().unwrap() = nonce;
+        self.nonce.store(nonce, Ordering::Release);
     }
 
     pub fn increment_nonce(&self, value: u64) {
-        *self.nonce.lock().unwrap() += value;
+        self.nonce.fetch_add(value, Ordering::AcqRel);
     }
 }