Dynamic Attach to Tomcat process fails with NullPointerException

[danbtl]

Attempting to attach to a Tomcat 9.0.4 process:

java -jar opentracing-specialagent-1.7.4.jar ${PID_OF_TOMCAT}

Throws the following Exception in the Tomcat process:

Terminating initialization of SpecialAgent due to:
java.lang.NullPointerException: Cannot invoke "java.lang.ClassLoader.getResourceAsStream(String)" because the return value of "java.lang.Thread.getContextClassLoader()" is null
	at io.opentracing.contrib.specialagent.AssembleUtil.loadProperties(AssembleUtil.java:881)
	at io.opentracing.contrib.specialagent.SpecialAgent.init(SpecialAgent.java:152)
	at io.opentracing.contrib.specialagent.SpecialAgent.premain(SpecialAgent.java:138)
	at io.opentracing.contrib.specialagent.SpecialAgent.premain(SpecialAgent.java:119)
	at io.opentracing.contrib.specialagent.SpecialAgent.agentmain(SpecialAgent.java:109)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
	at java.base/java.lang.reflect.Method.invoke(Method.java:577)
	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:491)
	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndCallAgentmain(InstrumentationImpl.java:513)

Java Version:

# java -version
openjdk version "18.0.1.1" 2022-04-22
OpenJDK Runtime Environment (build 18.0.1.1+2)
OpenJDK 64-Bit Server VM (build 18.0.1.1+2, mixed mode)

Not sure if I'm doing something wrong.