golang 1.5 shared library + ruby ffi

benchmark.rb

# 搭配 http://qiita.com/yanolab/items/1e0dd7fd27f19f697285 服用
require 'ffi'                                                                                                                           
require 'benchmark'                                                                                                                     
                                                                                                                                        
module LibGo                                                                                                                            
  extend FFI::Library                                                                                                                   
  ffi_lib './libgo.so'                                                                                                                  
  attach_function :fib, [:int], :int                                                                                                    
                                                                                                                                        
end                                                                                                                                     
                                                                                                                                        
def fib(i)                                                                                                                              
  return i if i < 2                                                                                                                     
  return fib(i-2)+fib(i-1)                                                                                                              
end                                                                                                                                     
                                                                                                                                        
n=10000                                                                                                                                 
Benchmark.bm do |x|                                                                                                                     
  x.report{ n.times{ fib(16); }}                                                                                                        
  x.report{ n.times{ LibGo.fib(16) }}                                                                                                   
end     

result

  user     system      total        real
1.130000   0.000000   1.130000 (  1.132376)
0.060000   0.000000   0.060000 (  0.068342)

Hi, I have been trying to find out how do exactly this, how did you create libgo.so? Can't seem to find anywhere how to make the .so.