fix error code.

app/src/main/java/com/proxy/shadowsocksr/impl/crypto/CryptoManager.kt

@@ -3,6 +3,7 @@ package com.proxy.shadowsocksr.impl.crypto
 import com.proxy.shadowsocksr.impl.ImplUtils
 import com.proxy.shadowsocksr.impl.crypto.crypto.*
 import java.nio.charset.Charset
+import java.util.*
 
 object CryptoManager
 {
@@ -14,7 +15,7 @@ object CryptoManager
             Pair("chacha20", intArrayOf(32, 8)),
             Pair("rc4-md5", intArrayOf(16, 16)))
 
-    private val cachedKeys: Map<String, ByteArray> = mapOf()
+    private val cachedKeys: HashMap<String, ByteArray> = hashMapOf()
 
     fun getMatchCrypto(cryptMethod: String = "chacha20", password: String = "0"): AbsCrypto
     {
@@ -30,7 +31,7 @@ object CryptoManager
             val passbf = password.toByteArray(Charset.forName("UTF-8"))
             key = ByteArray(cryptMethodInfo[0])
             ImplUtils.EVP_BytesToKey(passbf, key)
-            cachedKeys.plus(Pair(k, key))
+            cachedKeys.put(k, key)
         }
         //
         if (cryptMethod.startsWith("aes-"))
@@ -41,9 +42,9 @@ object CryptoManager
         when (cryptMethod)
         {
             "salsa20" -> return SalsaCrypto(cryptMethod, key)
-            "rc4-md5" -> return RC4MD5Crypto(cryptMethod,key)
+            "rc4-md5" -> return RC4MD5Crypto(cryptMethod, key)
         //...
-            else -> return ChachaCrypto(cryptMethod, key)//default chacha20
+            else      -> return ChachaCrypto(cryptMethod, key)//default chacha20
         }
     }