Unexpected channel behavior

[spongehah]

For the following code, there may be two running results:
@luoliwoshang verified and obtained consistent results.

package main

import (
	"github.com/goplus/llgo/c"
)

func main() {
	res := make(chan struct{})
	done := make(chan struct{})
	go func() {
		println("go")
		//time.Sleep(4 * time.Second)
		//c.Usleep(4 * 1000 * 1000)
		select {
		case <-res:
			println("res")
		case <-done:
			println("done")
		}
	}()

	res <- struct{}{}
	c.Usleep(2 * 1000 * 1000)
	//time.Sleep(2 * time.Second)
}

(base) ~/go/src/llgo/x git:[refactor/c-libuv-remove-go-wrapper]
llgo run test.go
go
res
(base) ~/go/src/llgo/x git:[refactor/c-libuv-remove-go-wrapper]
llgo run test.go
go

environment:

(base) ~/go/src/llgo/x git:[refactor/c-libuv-remove-go-wrapper]
go version
go version go1.21.4 darwin/amd64

(base) ~/go/src/llgo/x git:[refactor/c-libuv-remove-go-wrapper]
uname -a
Darwin MacBook.local 22.6.0 Darwin Kernel Version 22.6.0: Mon Apr 22 20:54:28 PDT 2024; root:xnu-8796.141.3.705.2~1/RELEASE_X86_64 x86_64

(base) ~/go/src/llgo/x git:[refactor/c-libuv-remove-go-wrapper]
clang --version
Apple clang version 14.0.3 (clang-1403.0.22.14.1)
Target: x86_64-apple-darwin22.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin