why can't add Specialization template in this case

when I add MYClass Specialization template , in this case, it will come out compile error, like this:

pet@iZbp1aq6c9kbbder4q405mZ:~/template_class/template_demo/2part/2_7$ g++ main.cpp  test.cpp
/usr/bin/ld: /tmp/ccRiDoql.o: in function `MYClass<int>::func()':
test.cpp:(.text+0x0): multiple definition of `MYClass<int>::func()'; /tmp/ccvTW7yj.o:main.cpp:(.text+0x0): first defined here
collect2: error: ld returned 1 exit status

I can't find the reason. In this case, I add MYClass Specialization template, it also cause compile failed.I dont' know why. the details code is below like this: template.h

#ifndef __MYCLASS_H__
#define __MYCLASS_H__

#include <iostream>

template <typename T>
class MYClass
{
public:
    void func();
};

template <typename T>
void MYClass<T>::func()
{
    std::cout << "MYClass::func!" << std::endl;
}


template <>
class MYClass<int>
{
public:
    void func();
};


void MYClass<int>::func()
{
    std::cout << "MYClass<int>::func!" << std::endl;
}

template <typename T>
void myfunc(T v1, T v2)
{
    std::cout << v1 + v2 << std::endl;
}
#endif

test.cpp

#include <iostream>
#include "template.h"

using namespace std;

template class  MYClass<float>; 
template void myfunc(int v1, int v2); 

void funcTest()
{
    MYClass<float> a;
    a.func();
}

main.cpp

#include <iostream>
#include "template.h"

using namespace std;

extern template class  MYClass<float>; 
extern template void myfunc(int v1, int v2); 
int main()
{

    MYClass<float> mycls;
    mycls.func();
    myfunc<int>(1,2);
    return 0;

}

I can't understand,why can't add this into here, when it removed, compile passed

template <>
class MYClass<int>
{
public:
    void func();
};


void MYClass<int>::func()
{
    std::cout << "MYClass<int>::func!" << std::endl;
}