As we had previously mentioned, we do not want to store our secret environment variables in our code. In our case it is the Stripe secret key. In this chapter, we’ll look at how to do that.

We have a env.example file for this exact purpose.

Start by renaming the env.example file to env.yml and replace its contents with the following.

# Add the environment variables for the various stages

prod:
  stripeSecretKey: "STRIPE_PROD_SECRET_KEY"

default:
  stripeSecretKey: "STRIPE_TEST_SECRET_KEY"

Make sure to replace the STRIPE_PROD_SECRET_KEY and STRIPE_TEST_SECRET_KEY with the Secret key from the Setup a Stripe account chapter. In our case we only have the test versions of the Stripe Secret key, so both these will be the same.

Next, let’s add a reference to these.

Add the following in the custom: block of serverless.yml.

  # Load our secret environment variables based on the current stage.
  # Fallback to default if it is not in prod.
  environment: ${file(env.yml):${self:custom.stage}, file(env.yml):default}

The custom: block of our serverless.yml should look like the following:

custom:
  # Our stage is based on what is passed in when running serverless
  # commands. Or fallsback to what we have set in the provider section.
  stage: ${opt:stage, self:provider.stage}
  # Set the table name here so we can use it while testing locally
  tableName: ${self:custom.stage}-notes
  # Load our secret environment variables based on the current stage.
  # Fallback to default if it is not in prod.
  environment: ${file(env.yml):${self:custom.stage}, file(env.yml):default}

And add the following in the environment: block in your serverless.yml.

    stripeSecretKey: ${self:custom.environment.stripeSecretKey}

Your environment: block should look like this:

  # These environment variables are made available to our functions
  # under process.env.
  environment:
    tableName: ${self:custom.tableName}
    stripeSecretKey: ${self:custom.environment.stripeSecretKey}

A quick explanation on the above:

  • We are loading a custom variable called environment from the env.yml file. This is based on the stage (we are deploying to) using file(env.yml):${self:custom.stage}. But if that stage is not defined in the env.yml then we fallback to loading everything under the default: block using file(env.yml):default. So Serverless Framework checks if the first is available before falling back to the second.

  • We then use this to add it to our environment variables by adding stripeSecretKey to the environment: block using ${self:custom.environment.stripeSecretKey}. This makes it available as process.env.stripeSecretKey in our Lambda functions. You’ll recall this from the previous chapter.

Commit Our Changes

Now we need to ensure that we don’t commit our env.yml file to git. The starter project that we are using has the following in the .gitignore.

# Env
env.yml

This will tell Git to not commit this file.

Next let’s commit the rest of our changes.

$ git add .
$ git commit -m "Adding stripe environment variable"

Now we are ready to test our billing API.