All plugins must be located in the directory specified by the
configuration variable
proxy.config.plugin.plugin_dir, which is located in
the records.config file. The directory can be
specified as an absolute or relative path.
If a relative path is used, then the starting directory will be
the Traffic Server installation directory as specified in
/etc/traffic_server. The default value is
config/plugins, which tells Traffic Server to use the
directory plugins located in the same configuration directory as
records.config. It is common to use the default
directory. Be sure to place the shared library
hello-world.so inside the directory you have
configured.