Map Iteration Order is Non-Deterministic

Why This Happens

Go deliberately randomizes map iteration order to prevent developers from relying on it. If your tests or output depend on map order, they will fail intermittently. Always sort map keys explicitly when deterministic order is needed.

The Problem

func printConfig(config map[string]string) {
    for k, v := range config {
        fmt.Printf("%s=%s\n", k, v) // order changes each run
    }
}

The Fix

func printConfig(config map[string]string) {
    keys := make([]string, 0, len(config))
    for k := range config {
        keys = append(keys, k)
    }
    sort.Strings(keys)
    for _, k := range keys {
        fmt.Printf("%s=%s\n", k, config[k])
    }
}

Step-by-Step Fix

1. 1

   Identify the order dependency

   Find code that relies on map iteration order for output, comparison, or testing.

2. 2

   Extract and sort keys

   Collect the map keys into a slice and sort them.

3. 3

   Iterate in sorted order

   Range over the sorted keys and access the map values by key.