How to create multiple stages in serverless framwork

Use Serverless' $self reference interpolation which can include further interpolation.

Define a custom variable where necessary. You can also use a default value if the variable doesn't exist.

Example:

service: some-cache-updater

custom:
  functimeout:
    prod: 120
    uat: 60

provider:
    name: aws
    runtime: nodejs8.10
    stage: ${opt:stage, 'dev'}

functions: 
    scheduledUpdater:
    handler: handler.scheduledUpdater
    # Lookup stage key from custom.functimeout. If it doesn't exist
    # default to 10
    timeout: ${self:custom.functimeout.${self:provider.stage}, '10'}

Then, when you deploy you can pass the --stage prod or --stage uat argument. In this example, no setting the stage will default to dev

serverless.yml:

...
provider:
  stage: ${opt:stage, 'dev'}
...

Command line:

sls deploy --stage prod

${opt:stage, 'dev'} takes the value passed from command line --stage option. In this case prod. If no option is passed dev is taken as default.

More info here: https://serverless.com/framework/docs/providers/aws/guide/variables/#recursively-reference-properties