Follow-up to https://bz.apache.org/bugzilla/show_bug.cgi?id=58313

Fix concurrent access of encoders map when clearing encoders prior to switch to async.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1701093 13f79535-47bb-0310-9956-ffa450edef68

java/org/apache/catalina/connector/InputBuffer.java

@@ -21,7 +21,7 @@
 import java.security.AccessController;
 import java.security.PrivilegedActionException;
 import java.security.PrivilegedExceptionAction;
-import java.util.HashMap;
+import java.util.concurrent.ConcurrentHashMap;
 
 import javax.servlet.ReadListener;
 
@@ -104,7 +104,7 @@ public class InputBuffer extends Reader
     /**
      * List of encoders.
      */
-    protected final HashMap<String,B2CConverter> encoders = new HashMap<>();
+    protected final ConcurrentHashMap<String,B2CConverter> encoders = new ConcurrentHashMap<>();
 
 
     /**