client: allow empty address for the system-default value

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>

client/client.go

@@ -4,6 +4,7 @@ import (
 	"time"
 
 	controlapi "github.com/moby/buildkit/api/services/control"
+	"github.com/moby/buildkit/util/appdefaults"
 	"github.com/pkg/errors"
 	"google.golang.org/grpc"
 )
@@ -14,7 +15,7 @@ type Client struct {
 
 type ClientOpt interface{}
 
-// New returns a new buildkit client
+// New returns a new buildkit client. Address can be empty for the system-default address.
 func New(address string, opts ...ClientOpt) (*Client, error) {
 	gopts := []grpc.DialOption{
 		grpc.WithInsecure(),
@@ -27,6 +28,9 @@ func New(address string, opts ...ClientOpt) (*Client, error) {
 			gopts = append(gopts, grpc.WithBlock(), grpc.FailOnNonTempDialError(true))
 		}
 	}
+	if address == "" {
+		address = appdefaults.Socket
+	}
 	conn, err := grpc.Dial(dialAddress(address), gopts...)
 	if err != nil {
 		return nil, errors.Wrapf(err, "failed to dial %q . make sure buildd is running", address)