# Goth
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Google + Auth = Goth
A simple library to generate and retrieve OAuth2 tokens for use with Google Cloud Service accounts.
## Installation
**Note:** below are instructions for using Goth v1.3+. For more information on earlier versions of Goth, [see v1.2.0 documentation on hexdocs.pm](https://hexdocs.pm/goth/1.2.0).
1. Add `:goth` to your list of dependencies in `mix.exs`. To use the built-in, Hackney-based HTTP
client adapter, add `:hackney` too:
```elixir
def deps do
[
{:goth, "~> 1.3-rc"},
{:hackney, "~> 1.17"}
]
end
```
2. Add Goth to your supervision tree:
```elixir
defmodule MyApp.Application do
use Application
def start(_type, _args) do
credentials = "GOOGLE_APPLICATION_CREDENTIALS_JSON" |> System.fetch_env!() |> Jason.decode!()
source = {:service_account, credentials, []}
children = [
{Goth, name: MyApp.Goth, source: source}
]
Supervisor.start_link(children, strategy: :one_for_one)
end
end
```
3. Fetch the token:
```elixir
iex> {:ok, token} = Goth.fetch(MyApp.Goth)
iex> token
%Goth.Token{
expires: 1453356568,
token: "ya29.cALlJ4ICWRvMkYB-WsAR-CZnExE459PA7QPqKg5nei9y2T9-iqmbcgxq8XrTATNn_BPim",
type: "Bearer",
...
}
```
See `Goth.start_link/1` for more information about possible configuration options.
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## Upgrading from Goth < 1.3
Earlier versions of Goth relied on global application environment configuration which is deprecated
in favour of a more direct and explicit approach in Goth v1.3+. Previously, we were depending
on the HTTPoison HTTP client, now we have an _optional_ dependency on Hackney, so in order
to use it, you need to explicitly include it in your dependencies too:
Change your `mix.exs`:
```elixir
def deps do
[
{:goth, "~> 1.3-rc"},
{:hackney, "~> 1.17"}
]
end
```
You might have code similar to this:
```elixir
# config/config.exs
config :goth,
json: {:system, "GCP_CREDENTIALS"}
```
```elixir
# lib/myapp.ex
defmodule MyApp do
def gcloud_authorization() do
{:ok, token} = Goth.Token.for_scope("https://www.googleapis.com/auth/cloud-platform.read-only")
"#{token.type} #{token.token}"
end
end
```
Replace it with:
```elixir
defmodule MyApp.Application do
@moduledoc false
use Application
def start(_type, _args) do
credentials = "GCP_CREDENTIALS" |> System.fetch_env!() |> Jason.decode!()
scopes = ["https://www.googleapis.com/auth/cloud-platform.read-only"]
source = {:service_account, credentials, scopes: scopes}
children = [
{Goth, name: MyApp.Goth, source: source}
]
Supervisor.start_link(children, strategy: :one_for_one)
end
end
```
```elixir
# lib/myapp.ex
defmodule MyApp do
def gcloud_authorization() do
{:ok, token} = Goth.fetch(MyApp.Goth)
"#{token.type} #{token.token}"
end
end
```
For more information on earlier versions of Goth, [see v1.2.0 documentation on hexdocs.pm](https://hexdocs.pm/goth/1.2.0).
