Update Tutorial-ExpressGraphQL.md

Author: Didier Franc

site/graphql-js/Tutorial-ExpressGraphQL.md

@@ -10,7 +10,7 @@ next: /graphql-js/graphql-clients/
 The simplest way to run an GraphQL API server is to use [Express](https://expressjs.com), a popular web application framework for Node.js. You will need to install two additional dependencies:
 
 ```bash
-npm install express express-graphql --save
+npm install express express-graphql graphql --save
 ```
 
 Let's modify our “hello world” example so that it's an API server rather than a script that runs a single query. We can use the 'express' module to run a webserver, and instead of executing a query directly with the `graphql` function, we can use the `express-graphql` library to mount a GraphQL API server on the “/graphql” HTTP endpoint: