Backgroundrb devel - Mar 2007 - example standalone error ... but if i ...

If I add .instance in front of new_worker I get the following error ... but
for some reason i cant call new_worker directly...?

error:
ruby sample_app.rb
my sample app :)
./backgroundrb/middleman.rb:440:in `ex'': undefined method
`synchronize'' for
nil:NilClass (NoMethodError)
        from ./backgroundrb/middleman.rb:401:in `[]''
        from ./backgroundrb/middleman.rb:461:in `gen_key''
        from ./backgroundrb/middleman.rb:173:in `new_worker''
        from ./backgroundrb/middleman.rb:173:in `new_worker''
        from sample_app.rb:9

code:
key = MiddleMan.instance.new_worker(:class => :example_worker)
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