lib.h

struct my {
	void (*f)();
};

main.go

package main

/*
#include "wrapper.h"
*/
import "C"

import (
	"fmt"
)

//export goF
func goF() {
	fmt.Printf("Hello from goF\n")
}

func main() {
	m := C.generate_my()
	fmt.Printf("%#v\n", m)
	m.f()
}

wrapper.c

#include "wrapper.h"

extern void goF();

struct my generate_my() {
	struct my res = {goF};
	return res;
}

wrapper.h

#include "lib.h"

struct my generate_my();