The http://www.modulecounts.com/ site counts the number of distributions on CPAN, which probably is the closest measure for comparisons with number of projects given on PyPI, RubyGems, etc.

However GoDoc seems to be showing number of package namespaces. If so this would be more comparable to the module count on CPAN (see http://www.cpan.org/)

So at this point in time we have:

  GoDoc:         36,497
  CPAN dists:    30,216 
  CPAN modules: 137,603