How to Sort Map by Key in Go: Simple Guide with Example

In Go, maps are unordered, so to sort a map by key, you first extract the keys into a slice, then use sort.Strings (or sort.Ints for int keys) to sort that slice. Finally, iterate over the sorted keys to access map values in order.

Syntax

To sort a map by key in Go, follow these steps:

• Extract keys from the map into a slice.
• Use sort.Strings(keys) or sort.Ints(keys) to sort the keys slice.
• Loop over the sorted keys to access map values in sorted order.

go

keys := make([]string, 0, len(myMap))
for k := range myMap {
    keys = append(keys, k)
}
sort.Strings(keys)
for _, k := range keys {
    fmt.Println(k, myMap[k])
}

Example

This example shows how to sort a map with string keys and print its keys and values in ascending order.

go

package main

import (
    "fmt"
    "sort"
)

func main() {
    myMap := map[string]int{
        "banana": 3,
        "apple": 5,
        "orange": 2,
        "grape": 4,
    }

    // Extract keys
    keys := make([]string, 0, len(myMap))
    for k := range myMap {
        keys = append(keys, k)
    }

    // Sort keys
    sort.Strings(keys)

    // Print map in sorted order
    for _, k := range keys {
        fmt.Printf("%s: %d\n", k, myMap[k])
    }
}

Output

apple: 5
banana: 3
grape: 4
orange: 2

Common Pitfalls

Maps in Go do not maintain order, so trying to iterate directly over a map expecting sorted keys will not work.

Also, sorting keys requires creating a separate slice; you cannot sort the map itself.

Remember to use the correct sort function matching your key type, like sort.Strings for strings or sort.Ints for integers.

go

package main

import (
    "fmt"
)

func main() {
    myMap := map[string]int{"b": 2, "a": 1}

    // Wrong: iterating map directly (order not guaranteed)
    for k, v := range myMap {
        fmt.Println(k, v)
    }

    // Right: extract keys and sort
    // ... (see previous example)
}

Output

b 2
a 1

Quick Reference

Step	Description	Function/Method
1	Extract keys from map	for k := range myMap { keys = append(keys, k) }
2	Sort keys slice	sort.Strings(keys) or sort.Ints(keys)
3	Iterate sorted keys	for _, k := range keys { use myMap[k] }

Key Takeaways

Maps in Go are unordered; sorting requires extracting keys into a slice.

Use sort.Strings or sort.Ints depending on the key type to sort the keys slice.

Iterate over the sorted keys slice to access map values in order.

Direct iteration over a map does not guarantee any order.

Always match the sort function to the key type for correct sorting.