How do I use HttpService:GetAsync() headers?

How do I use the authorization header to fit both username / password in?

Authorization headers are declared as a dictionary.

local httpService = game:GetService("HttpService")

local url = "https://example.com" --url
local headers = {} --dictionary of authorization headers

local success, result = pcall(function()
    return httpService:GetAsync(url, false, headers)
end)

if success then
    --do code
else
    warn(result)
end