How to create a case insensitive map in Go?

Question

I want to have a key insensitive string as key. Is it supported by the language or do I have to create it myself? thank you

Edit: What I am looking for is a way to make it by default instead of having to remember to convert the keys every time I use the map.

Answer 1

Edit: My initial code actually still allowed map syntax and thus allowed the methods to be bypassed. This version is safer.

You can "derive" a type. In Go we just say declare. Then you define methods on your type. It just takes a very thin wrapper to provide the functionality you want. Note though, that you must call get and set with ordinary method call syntax. There is no way to keep the index syntax or optional ok result that built in maps have.

package main

import (
    "fmt"
    "strings"
)

type ciMap struct {
    m map[string]bool
}

func newCiMap() ciMap {
    return ciMap{m: make(map[string]bool)}
}

func (m ciMap) set(s string, b bool) {
    m.m[strings.ToLower(s)] = b
}

func (m ciMap) get(s string) (b, ok bool) {
    b, ok = m.m[strings.ToLower(s)]
    return
}

func main() {
    m := newCiMap()
    m.set("key1", true)
    m.set("kEy1", false)
    k := "keY1"
    b, _ := m.get(k)
    fmt.Println(k, "value is", b)
}