Amplify-cli: can't update graphql api key

[gangok]

* Which Category is your question related to? *
API

* What AWS Services are you utilizing? *
AppSync

* Provide additional details e.g. code snippets *
I created graphql api with api key auth type about a week ago. After the first key is expired, every call to the api from my frontend code(using aws-exports.js file) obviously fails.
What I have tried was to make a new api key in appsync console, and modified my local file into new key, but it was overritten by the old api key whenever I modify something in my api and perform amplify publish
I also tried amplify api update as suggested in #242, but It didn't affect anything.
Besides deleting and making a new api, how can I update graphql api key on my amplify project?

[mikeparisstuff]

Support for this is added in #446.