internal/localdatasource: correctly initialize DataSource.sourceClient

Create a valid source.Client to avoid nil pointer dereference while
processing packages.

Change-Id: Id19a2ba07cfac8de85c9386a069d100b907421d2
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/280619
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
diff --git a/internal/localdatasource/datasource.go b/internal/localdatasource/datasource.go
index 83e029a..96d63a6 100644
--- a/internal/localdatasource/datasource.go
+++ b/internal/localdatasource/datasource.go
@@ -15,6 +15,7 @@
 	"path/filepath"
 	"strings"
 	"sync"
+	"time"
 
 	"golang.org/x/pkgsite/internal"
 	"golang.org/x/pkgsite/internal/derrors"
@@ -35,6 +36,7 @@
 // checks by default.
 func New() *DataSource {
 	return &DataSource{
+		sourceClient:  source.NewClient(1 * time.Minute),
 		loadedModules: make(map[string]*internal.Module),
 	}
 }