Add async/await example to 1-project-structure.md (#104)

Author: the-wunmi

Diff for: content/guides/1-project-structure.md

@@ -156,4 +156,42 @@ module.exports = {
 }
 ```
 
+Using async/await:
+
+```
+module.exports = {
+  async query(text, params) {
+    const start = Date.now()
+    const res = await pool.query(text, params)
+    const duration = Date.now() - start
+    console.log('executed query', { text, duration, rows: res.rowCount })
+    return res
+  },
+
+  async getClient() {
+    const client = await pool.connect()
+    const query = client.query
+    const release = client.release
+    // set a timeout of 5 seconds, after which we will log this client's last query
+    const timeout = setTimeout(() => {
+      console.error('A client has been checked out for more than 5 seconds!')
+      console.error(`The last executed query on this client was: ${client.lastQuery}`)
+    }, 5000)
+    // monkey patch the query method to keep track of the last query executed
+    client.query = (...args) => {
+      client.lastQuery = args
+      return query.apply(client, args)
+    }
+    client.release = () => {
+      // clear our timeout
+      clearTimeout(timeout)
+      // set the methods back to their old un-monkey-patched version
+      client.query = query
+      client.release = release
+      return release.apply(client)
+    }
+    return client
+  }
+}
+```
 That should hopefully give us enough diagnostic information to track down any leaks.