The config that panics on write

medium

LoadDefaults is supposed to return a config map with defaults applied, and callers then add their own keys. It compiles, it reads fine, and it panics the moment anyone writes to it. Fix it so the returned map is usable.

Signature

func LoadDefaults(overrides map[string]string) map[string]string

Examples

LoadDefaults(nil) → {"region":"eu-central-1","retries":"3"}
LoadDefaults(map[string]string{"retries":"5"}) → retries overridden to "5"
the returned map must accept new keys without panicking

Constraints

Defaults are region=eu-central-1 and retries=3
Any key in overrides wins over the defaults, including keys that are not defaults
Do not modify the overrides map the caller passed in

package main

// LoadDefaults returns the default config with overrides applied.
//
// BUG: cfg is declared but never made, so it is a nil map. Reads work, but the
// first write panics with "assignment to entry in nil map".
func LoadDefaults(overrides map[string]string) map[string]string {
	var cfg map[string]string
	for k, v := range overrides {
		cfg[k] = v
	}
	if _, ok := cfg["region"]; !ok {
		cfg["region"] = "eu-central-1"
	}
	if _, ok := cfg["retries"]; !ok {
		cfg["retries"] = "3"
	}
	return cfg
}

See what a pass includes Try the question demo