error output

# _/Users/larz/Programming/random
duplicate symbol __Z3addii in:
    /var/folders/kz/fgkgncp17mg8t84dm5jjvzvm0000gn/T//go-link-Vas0Gn/000000.o
    /var/folders/kz/fgkgncp17mg8t84dm5jjvzvm0000gn/T//go-link-Vas0Gn/000001.o
ld: 1 duplicate symbol for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
/usr/local/go/pkg/tool/darwin_amd64/6l: running clang failed: unsuccessful exit status 0x100

main.cc

#include "main.hh"

int add(int first, int second) {
  return first + second;
}

main.go

package main

import "C"

func main() {
	println(Add(1, 2))
}

main.hh

#ifndef H_MAIN
#define H_MAIN 1

int add(int, int);

#endif

main.swigcxx

%module main

%{
#include "main.hh"
%}

%include "main.hh"