@Override
	public String getBaseListenerFileName(SourceType sourceType) {
		CodeGenerator gen = getCodeGenerator();
		Grammar g = gen.g;
		assert g.name != null;
		return g.name.toLowerCase()+"_base_listener.go";
	}
A given grammar T, return a blank listener implementation
 such as TBaseListener.java, if we're using the Java target.
tool/src/org/antlr/v4/codegen/target/GoTarget.java