optimize the signer

shared/src/commonMain/kotlin/su/reya/coop/Signer.kt

@@ -7,34 +7,37 @@ import rust.nostr.sdk.AsyncNostrSigner
 import rust.nostr.sdk.Event
 import rust.nostr.sdk.PublicKey
 import rust.nostr.sdk.UnsignedEvent
+import kotlin.concurrent.Volatile
 import kotlin.time.Duration.Companion.seconds
 
 class UniversalSigner(initialSigner: AsyncNostrSigner) : AsyncNostrSigner {
     private val mutex = Mutex()
+
+    @Volatile
     private var signer: AsyncNostrSigner = initialSigner
 
+    @Volatile
     var currentUser: PublicKey? = null
         private set
 
     /**
      * Get the current signer.
      */
-    suspend fun get(): AsyncNostrSigner = mutex.withLock {
-        signer
-    }
+    fun get(): AsyncNostrSigner = signer
 
     /**
      * Switch to a new signer.
      */
     suspend fun switch(newSigner: AsyncNostrSigner) = mutex.withLock {
-        signer = newSigner
-        try {
-            currentUser = withTimeoutOrNull(20.seconds) {
+        val pubkey = try {
+            withTimeoutOrNull(20.seconds) {
                 newSigner.getPublicKeyAsync()
             }
         } catch (e: Exception) {
             throw IllegalStateException("Failed to get public key from signer", e)
         }
+        signer = newSigner
+        currentUser = pubkey
     }
 
     override suspend fun getPublicKeyAsync(): PublicKey? {