multiple definition error when linking C++ dynamic library and Go with SWIG

I would like to know the procedure to link the 3rd party dynamic
library, written in C++, and Go source code.
I have only C++ header files and shared library files(*.hh and *.so).
I do not have C++ source files(*.cc).

For a test purpose, I set up 3 repositories.

(1)https://github.com/hsmtkk/swigo_cc
The C++ program.

(2)https://github.com/hsmtkk/swigo_bridge
The program to bridge C++ and Go with SWIG.

(3)https://github.com/hsmtkk/swigo_user
The Go program.

For the codes in (2) and (3), C++ source files(*.cc) are not available.

This is my swigcxx file, included in the (2) repository.
https://github.com/hsmtkk/swigo_bridge/blob/main/example.swigcxx
```
%module example
%{
#include "example.hh"
%}
%include "example.hh"
```

This is my command to generate wrapper files in the (2) repository.
https://github.com/hsmtkk/swigo_bridge/blob/main/Makefile
```
swig -go -cgo -c++ -intgosize 64 -use-shlib -soname libexample.so
example.swigcxx
```

When I try to build the (3) program, I get this error.
```
$ go build
# github.com/hsmtkk/swigo_bridge
example.swigcxx:5: Error: Unable to find 'example.hh'
```

When I include the header file manually, I get another error.
```
$ env CGO_CXXFLAGS="-I`pwd`" go build
# github.com/hsmtkk/swigo_bridge
/tmp/go-build130079447/b002/_x005.o: In function
`_wrap_Swig_free_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0x83): multiple definition of
`_wrap_Swig_free_example_fe57d0301a1c3822'
/tmp/go-build130079447/b002/_x004.o:example_wrap.cxx:(.text+0x83):
first defined here
/tmp/go-build130079447/b002/_x005.o: In function
`_wrap_Swig_malloc_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0xad): multiple definition of
`_wrap_Swig_malloc_example_fe57d0301a1c3822'
/tmp/go-build130079447/b002/_x004.o:example_wrap.cxx:(.text+0xad):
first defined here
/tmp/go-build130079447/b002/_x005.o: In function
`_wrap_new_Example_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0xe4): multiple definition of
`_wrap_new_Example_example_fe57d0301a1c3822'
/tmp/go-build130079447/b002/_x004.o:example_wrap.cxx:(.text+0xe4):
first defined here
/tmp/go-build130079447/b002/_x005.o: In function
`_wrap_Example_GetNumber_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0x14d): multiple definition of
`_wrap_Example_GetNumber_example_fe57d0301a1c3822'
/tmp/go-build130079447/b002/_x004.o:example_wrap.cxx:(.text+0x14d):
first defined here
/tmp/go-build130079447/b002/_x005.o: In function
`_wrap_delete_Example_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0x187): multiple definition of
`_wrap_delete_Example_example_fe57d0301a1c3822'
/tmp/go-build130079447/b002/_x004.o:example_wrap.cxx:(.text+0x187):
first defined here
/tmp/go-build130079447/b002/_x004.o: In function
`_wrap_new_Example_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0x118): undefined reference to `Example::Example(int)'
/tmp/go-build130079447/b002/_x004.o: In function
`_wrap_Example_GetNumber_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0x171): undefined reference to `Example::GetNumber()'
/tmp/go-build130079447/b002/_x005.o: In function
`_wrap_new_Example_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0x118): undefined reference to `Example::Example(int)'
/tmp/go-build130079447/b002/_x005.o: In function
`_wrap_Example_GetNumber_example_fe57d0301a1c3822':
example_wrap.cxx:(.text+0x171): undefined reference to `Example::GetNumber()'
collect2: error: ld returned 1 exit status
```

How can I solve the issue above?

I would appreciate your help.
Best regards,

[email protected]