diff --git a/packages/analytics/src/trackers/SessionTracker.ts b/packages/analytics/src/trackers/SessionTracker.ts
index 2ab7cba95da..3a6a2b0e0a4 100644
--- a/packages/analytics/src/trackers/SessionTracker.ts
+++ b/packages/analytics/src/trackers/SessionTracker.ts
@@ -11,7 +11,7 @@
  * and limitations under the License.
  */
 
- // the session tracker for web
+// the session tracker for web
 
 import { ConsoleLogger as Logger, Hub, JS } from '@aws-amplify/core';
 import { SessionTrackOpts } from '../types';
@@ -36,7 +36,7 @@ export default class SessionTracker {
     constructor(tracker, opts) {
         this._config = Object.assign({}, defaultOpts, opts);
         this._tracker = tracker;
-        
+
         this._hasEnabled = false;
         this._trackFunc = this._trackFunc.bind(this);
         this._trackBeforeUnload = this._trackBeforeUnload.bind(this);
@@ -71,8 +71,9 @@ export default class SessionTracker {
     }
 
     private async _trackFunc() {
-        const customAttrs = typeof this._config.attributes === 'function'? 
+        const customAttrs = typeof this._config.attributes === 'function' ?
             await this._config.attributes() : this._config.attributes;
+
         const attributes = Object.assign(
             {},
             customAttrs
@@ -80,7 +81,7 @@ export default class SessionTracker {
 
         if (document[this._hidden]) {
             this._tracker(
-                { 
+                {
                     name: '_session.stop',
                     attributes
                 },
@@ -90,7 +91,7 @@ export default class SessionTracker {
             });
         } else {
             this._tracker(
-                { 
+                {
                     name: '_session.start',
                     attributes
                 },
@@ -102,16 +103,18 @@ export default class SessionTracker {
     }
 
     private _trackBeforeUnload() {
-        const getCustomAttrs = typeof this._config.attributes === 'function'? 
-            this._config.attributes() : Promise.resolve(this._config.attributes);
-      
-        getCustomAttrs.then((customAttrs) => {
+        // before unload callback cannot be async => https://github.com/aws-amplify/amplify-js/issues/2088
+        const customAttrs = typeof this._config.attributes === 'function' ?
+            Promise.resolve(this._config.attributes()) : Promise.resolve(this._config.attributes);
+
+        customAttrs.then(custom => {
             const attributes = Object.assign(
                 {},
-                customAttrs
+                custom
             );
+
             this._tracker(
-                { 
+                {
                     name: '_session.stop',
                     attributes,
                     immediate: true
@@ -121,6 +124,7 @@ export default class SessionTracker {
                 logger.debug('record session stop event failed.', e);
             });
         });
+
     }
 
     // to keep configure a synchronized function
@@ -131,8 +135,8 @@ export default class SessionTracker {
         } else {
             initialEventSent = true;
         }
-        
-        const customAttrs = typeof this._config.attributes === 'function'? 
+
+        const customAttrs = typeof this._config.attributes === 'function' ?
             await this._config.attributes() : this._config.attributes;
         const attributes = Object.assign(
             {},
@@ -140,7 +144,7 @@ export default class SessionTracker {
         );
 
         this._tracker(
-            { 
+            {
                 name: '_session.start',
                 attributes
             },
diff --git a/packages/analytics/src/types/Analytics.ts b/packages/analytics/src/types/Analytics.ts
index 887f0168a32..bacae23a1cc 100644
--- a/packages/analytics/src/types/Analytics.ts
+++ b/packages/analytics/src/types/Analytics.ts
@@ -23,7 +23,7 @@ export interface AnalyticsOptions {
 }
 
 export interface EventAttributes {
-    [key: string]: any;
+    [key: string]: string;
 }
 
 export interface EventMetrics {
@@ -35,7 +35,7 @@ export interface pageViewTrackOpts {
     type?: string
     eventName?: string,
     provider?: string,
-    attributes?: EventAttributes | (()=> EventAttributes),
+    attributes?: EventAttributes | (()=> EventAttributes | Promise<EventAttributes>),
     getUrl?: (() => string)
 }
 
@@ -44,11 +44,11 @@ export interface EventTrackOpts {
     events?: Array<string>,
     selectorPrefix?: string,
     provider?: string,
-    attributes?: EventAttributes | (()=> EventAttributes)
+    attributes?: EventAttributes | (()=> EventAttributes | Promise<EventAttributes>)
 }
 
 export interface SessionTrackOpts {
     enable: boolean,
-    attributes?: EventAttributes | (()=> EventAttributes),
+    attributes?: EventAttributes | (()=> EventAttributes | Promise<EventAttributes>),
     provider?: string,
 }