Ran `go run .` and it ended with:

   [...]
   go: downloading github.com/mewmew/float v0.0.0-20181121163145-c0f786d7da73    
   go: downloading github.com/pkg/errors v0.8.0                                  
   go: downloading github.com/rickypai/natsort v0.0.0-20180124032556-f194e6bd5b0c
   @$const_str = global [16 x i8] c"Hello world %d\0A\00"                        
                                                                                 
   declare void @printf(...)                                                     
                                                                                 
   define void @main() {                                                         
   0:                                                                            
       %0 = add i64 30, 12                                                       
       call void (...) @printf([16 x i8]* @$const_str, i64 %0)                   
       ret void                                                                  
   }                                                                             
   0>