// src/os/proc.go 68行
func runtime_beforeExit() // implemented in runtime

// os_beforeExit is called from os.Exit(0).
//go:linkname os_beforeExit os.runtime_beforeExit
func os_beforeExit() {
  if raceenabled {
    racefini()
  }
}

$mkdir hello
$mkdir link

$cd hello
// 函数签名
$vim hello.go
package hello
import (
  _ "demo/link"
)
func Hello()
// 函数体
$vim link.go
package link
import _ "unsafe"
//go:linkname helloWorld demo/hello.Hello
func helloWorld() {
  println("hello world!")
}

$cd demo
vim demo.go
package main
import (
  "demo/hello"
)
func main() {
  hello.Hello()
}

go run demo.go
# demo/hello
hello/hello.go:7:6: missing function body

$cd hello && touch aa.s
$go run demo.go
hello world!