Go - check if a channel is closed without read

chan.go

package main

import (
	"fmt"
	"unsafe"
)

// Copy of hchan struct with first necessary fields.
// See: "src/runtime/chan.go"
type hchan struct {
	qcount   uint           // total data in the queue
	dataqsiz uint           // size of the circular queue
	buf      unsafe.Pointer // points to an array of dataqsiz elements
	elemsize uint16
	closed   uint32
}

// IsClosed checks whether a passed channel is closed.
//
// Warning: possible race conditions ahead as it doesn't respect inner semaphore.
func IsClosed[T any](ch chan T) bool {
	sChan := (*hchan)(unsafe.Pointer(*(*unsafe.Pointer)(unsafe.Pointer(&ch))))
	return sChan.closed != 0
}

func main() {
	ch := make(chan int, 2)
	fmt.Println("IsClosed:", IsClosed(ch))

	close(ch)
	fmt.Println("IsClosed:", IsClosed(ch))
}