New goroutine leak profiler experiment

// This program demonstrates how to collect a goroutine leak profile
// using the experimental flag.  It does not compile in Go 1.27.1
// because the flag is not yet implemented.  Run it with
// GOEXPERIMENT=goroutineleakprofile ./prog to see the effect.

package main

import (
	"fmt"
	"os"
	"runtime/pprof"
)

func main() {
	// Create a file to store the leak profile.
	f, err := os.Create("goroutineleak.pprof")
	if err != nil {
		fmt.Println("error creating file:", err)
		return
	}
	defer f.Close()

	// Lookup the leak profile by name.
	prof := pprof.Lookup("goroutineleak")
	if prof == nil {
		fmt.Println("goroutineleak profile not available")
		return
	}

	// Write the profile data to the file.
	if err := prof.WriteTo(f, 1); err != nil {
		fmt.Println("error writing profile:", err)
		return
	}

	fmt.Println("goroutine leak profile written to goroutineleak.pprof")
}