Policy for removing GODEBUG flags

// This program demonstrates how a GODEBUG flag is handled when it is
// marked as deprecated and then removed.  The flag "panicnil" is a
// real flag that existed in Go 1.21.  In this sandbox we simulate the
// deprecation logic by checking the flag value and printing a warning
// if it is set to a non‑default value.  The program then proceeds
// normally, ignoring the flag value because the flag has been removed
// in the current release.
//
// Note: In Go 1.27.1 the flag is still present, but the policy would
// have removed it in a future release.  This example shows the
// deprecation warning that would be emitted by tools.

package main

import (
	"fmt"
	"os"
)

func main() {
	// Read the GODEBUG environment variable.
	godebug := os.Getenv("GODEBUG")
	// For simplicity we only look for the "panicnil" flag.
	// In a real tool this would parse all flags.
	if godebug != "" {
		// Simulate deprecation: warn if panicnil is set to 1.
		if godebug == "panicnil=1" {
			fmt.Println("WARNING: panicnil is deprecated; setting it to 1 will be ignored.")
		}
	}
	// The rest of the program runs normally.
	fmt.Println("Program running with panicnil default (0).")
}