diff --git a/async_worker_group.go b/async_worker_group.go
index 3ed870a..d1a1e15 100644
--- a/async_worker_group.go
+++ b/async_worker_group.go
@@ -1,13 +1,14 @@
 package bqstreamer
 
 import (
-	"errors"
 	"net/http"
 	"sync"
 	"time"
 
 	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google"
 	"golang.org/x/oauth2/jwt"
+	"google.golang.org/api/bigquery/v2"
 )
 
 // AsyncWorkerGroup asynchronously streams rows to BigQuery in bulk.
@@ -50,11 +51,21 @@ type AsyncWorkerGroup struct {
 }
 
 // New returns a new AsyncWorkerGroup using given OAuth2/JWT configuration.
+// Set jwtConfig to nil if your system corresponds to either of the following conditions:
+// - a system that has called "gcloud auth application-default login"
+// - a system running in Google Application Engine
+// - a system running in Google Compute Engine
+// ref: https://developers.google.com/identity/protocols/application-default-credentials
 func NewAsyncWorkerGroup(jwtConfig *jwt.Config, options ...AsyncOptionFunc) (*AsyncWorkerGroup, error) {
 	if jwtConfig == nil {
-		return nil, errors.New("jwt.Config is nil")
+		ctx := oauth2.NoContext
+		client, err := google.DefaultClient(ctx, bigquery.BigqueryInsertdataScope)
+		if err != nil {
+			return nil, err
+		}
+		newHTTPClient := func() *http.Client { return client }
+		return newAsyncWorkerGroup(newHTTPClient, options...)
 	}
-
 	// Create a new Streamer, with OAuth2/JWT http.Client constructor function.
 	newHTTPClient := func() *http.Client { return jwtConfig.Client(oauth2.NoContext) }
 	return newAsyncWorkerGroup(newHTTPClient, options...)
diff --git a/sync_worker.go b/sync_worker.go
index be21a6a..6a1663a 100644
--- a/sync_worker.go
+++ b/sync_worker.go
@@ -3,6 +3,7 @@
 package bqstreamer
 
 import (
+	"context"
 	"net/http"
 	"time"
 
@@ -146,16 +147,22 @@ func (w *SyncWorker) insertAll(insertFunc func(projectID, datasetID, tableID str
 // TODO cache bigquery service instead of creating a new one every insertTable() call
 // TODO add support for SkipInvalidRows, IgnoreUnknownValues
 func (w *SyncWorker) insertTable(projectID, datasetID, tableID string, tbl table) *TableInsertErrors {
-	res, err := bigquery.NewTabledataService(w.service).
-		InsertAll(
-			projectID, datasetID, tableID,
-			&bigquery.TableDataInsertAllRequest{
-				Kind:                "bigquery#tableDataInsertAllRequest",
-				Rows:                tbl,
-				IgnoreUnknownValues: w.ignoreUnknownValues,
-				SkipInvalidRows:     w.skipInvalidRows,
-			}).
-		Do()
+	tabledataInsertAllCall := bigquery.NewTabledataService(w.service).InsertAll(
+		projectID, datasetID, tableID,
+		&bigquery.TableDataInsertAllRequest{
+			Kind:                "bigquery#tableDataInsertAllRequest",
+			Rows:                tbl,
+			IgnoreUnknownValues: w.ignoreUnknownValues,
+			SkipInvalidRows:     w.skipInvalidRows,
+		})
+
+	// Set a timeout on the bigtable insert
+	// TODO make this configurable by passing through a context
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	tabledataInsertAllCall.Context(ctx)
+	res, err := tabledataInsertAllCall.Do()
 
 	var rows []*bigquery.TableDataInsertAllResponseInsertErrors
 	if res != nil {