[Deadlock] Move Agent-Version property reading away from the class loading stage (#436)

Author: wu-sheng

CHANGES.md

@@ -23,6 +23,7 @@ Release Notes.
 * Add support for KafkaClients 3.x.
 * Support to customize the collect period of JVM relative metrics.
 * Upgrade netty-codec-http2 to 4.1.86.Final.
+* Move `Agent-Version` property reading away from the class loading stage to avoid deadlock when use `jarsigner`.
 
 #### Documentation
 

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/remote/AgentIDDecorator.java

@@ -40,7 +40,7 @@
  */
 public class AgentIDDecorator implements ChannelDecorator {
     private static final ILog LOGGER = LogManager.getLogger(AgentIDDecorator.class);
-    private static final Metadata.Key<String> AGENT_VERSION_HEAD_HEADER_NAME = Metadata.Key.of("Agent-Version", Metadata.ASCII_STRING_MARSHALLER);
+    private static Metadata.Key<String> AGENT_VERSION_HEAD_HEADER_NAME;
     private String version = "UNKNOWN";
 
     public AgentIDDecorator() {
@@ -61,6 +61,7 @@ public AgentIDDecorator() {
                     }
                 }
             }
+            AGENT_VERSION_HEAD_HEADER_NAME = Metadata.Key.of("Agent-Version", Metadata.ASCII_STRING_MARSHALLER);
         } catch (Exception e) {
             LOGGER.warn("Can't read version from MANIFEST.MF in the agent jar");
         }