update server.js

-import { GraphQLServer } from "graphql-yoga";
 import dotenv from "dotenv";
 dotenv.config();
+import { GraphQLServer } from "graphql-yoga";
+import morgan from "morgan";
+import schema from "./schema";
 
-const PORT = process.env.PORT || 4000;
-
-const typeDefs = `
-    type Query {
-        hello(name: String): String
-    }
-`;
+const PORT = process.env.PORT;
 
-const resolvers = {
-  Query: {
-    hello: () => "hello",
-  },
-};
+const server = new GraphQLServer({ schema });
 
-const server = new GraphQLServer({ typeDefs, resolvers });
+server.express.use(morgan("dev"));
 
 server.start(() => console.log(`server is running : http://localhost:${PORT}`));