main.c

#ifdef __APPLE__
#include <machine/endian.h>
#include <libkern/OSByteOrder.h>
#define le32toh(x) OSSwapLittleToHostInt32(x)
#else
#include <endian.h>
#endif

#include "main.h"

inline int32_t decode_int32(int32_t source) {
    return le32toh(source);
}

int sample_func() {
  int ret = decode_int32(0xff00);
  return ret;
}

main.go

package main

// #cgo CFLAGS: -I${SRCDIR}/
// #include "main.h"
// #include <stdint.h>
import "C"

import "fmt"

func main() {
	res := C.sample_func()
	fmt.Printf("result=%d\n", res)
}

main.h

#ifndef MAIN_H
#define MAIN_H

int sample_func();

#endif // MAIN_H