`System.Text.Json` now supports Dictionaries with non-string keys

jsondictionarykeys.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
    <LangVersion>preview</LangVersion>
  </PropertyGroup>

</Project>

Program.cs

using System;
using System.Collections.Generic;
using System.Text.Json;

Dictionary<int, string> numbers = new ()
{
    {0, "zero"},
    {1, "one"},
    {2, "two"},
    {3, "three"},
    {5, "five"},
    {8, "eight"},
    {13, "thirteen"},
    {21, "twenty one"},
    {34, "thirty four"},
    {55, "fifty five"},
};

var json = JsonSerializer.Serialize<Dictionary<int, string>>(numbers);

Console.WriteLine(json);

var dictionary = JsonSerializer.Deserialize<Dictionary<int, string>>(json);

Console.WriteLine(dictionary[55]);

Produces the following output.

rich@thundera jsondictionarykeys % dotnet run
{"0":"zero","1":"one","2":"two","3":"three","5":"five","8":"eight","13":"thirteen","21":"twenty one","34":"thirty four","55":"fifty five"}
fifty five