queryHandler.ts

import { parse } from 'graphql/language';
import { execute } from 'graphql/execution';
import { validate } from 'graphql/validation';
import { schema } from '../graphql';

export const handler = async (event: APIGatewayEvent): Promise<ApiGatewayProxyResult> => {
   try {
      const body = JSON.parse(event.body || '');
      const parsed = parse(body.query);

      const validated = validate(schema, parsed);
      if (validated.length > 0)
         return okResponse({ errors: validated })
        
      const result = await execute({
         schema,
         document: parsed,
         variableValues: body.variables,
         contextValue: createContext(event),
      });
  
      return okResponse(result);
   } catch(err) {
      return badUserInput(err)
   }
};