ts-morph
Async
Certain nodes in TypeScript can have an async keyword modifier.
Is async
A node can be tested if it's async using the isAsync() method:
functionDeclaration.isAsync(); // returns: boolean
async keyword
Get the async keyword if it exists:
functionDeclaration.getAsyncKeyword();
Set async
Set if the declaration is async using setIsAsync:
functionDeclaration.setIsAsync(true);