add timeout for AWS MetadataAccessor (#318)

* add timeout for awsMetadataAccessor

* style fix

Author: mayurkale22

packages/opencensus-resource-util/src/resource-utils.ts

@@ -123,7 +123,12 @@ export async function getAwsEC2Resource(): Promise<Resource> {
  */
 async function awsMetadataAccessor<T>(): Promise<T> {
   return new Promise((resolve, reject) => {
+    const timeoutId = setTimeout(() => {
+      reject(new Error('EC2 metadata api request timed out.'));
+    }, 2000);
+
     const req = http.get(AWS_INSTANCE_IDENTITY_DOCUMENT_URI, (res) => {
+      clearTimeout(timeoutId);
       const {statusCode} = res;
       res.setEncoding('utf8');
       let rawData = '';
@@ -142,7 +147,10 @@ async function awsMetadataAccessor<T>(): Promise<T> {
         }
       });
     });
-    req.on('error', (err) => reject(err));
+    req.on('error', (err) => {
+      clearTimeout(timeoutId);
+      reject(err);
+    });
   });
 }