golang:cgo extern无法正常工作

我正在尝试使用以下示例为golang运行cgo(在go-wiki - > Global Functions中给出):

foo.go 文件:

package gocallback

import "fmt"

/*
#include 
extern void ACFunction();
*/
import "C"

//export AGoFunction
func AGoFunction() {
        fmt.Println("AGoFunction()")
}

func Example() {
        C.ACFunction()
}

foo.c 文件:

#include "_cgo_export.h"
void ACFunction() {
    printf("ACFunction()\n");
    AGoFunction();
}

运行此示例时,我收到以下错误:

# command-line-arguments
/tmp/go-build770916112/command-line-arguments/_obj/foo.cgo2.o: In function    `_cgo_3234419c4c2a_Cfunc_ACFunction':
./foo.go:36: undefined reference to `ACFunction'
collect2: ld returned 1 exit status

我无法追查这一点.为什么ACFunction是undefined？还是我错过了什么？

go version:go go go1.1.2 linux/386