Merge pull request #982 from tiborvass/fix-stdin-blocking

session: add lock to fix hang

session/auth/authprovider/authprovider.go

@@ -3,6 +3,7 @@ package authprovider
 import (
 	"context"
 	"io/ioutil"
+	"sync"
 
 	"github.com/docker/cli/cli/config"
 	"github.com/docker/cli/cli/config/configfile"
@@ -19,13 +20,21 @@ func NewDockerAuthProvider() session.Attachable {
 
 type authProvider struct {
 	config *configfile.ConfigFile
+
+	// The need for this mutex is not well understood.
+	// Without it, the docker cli on OS X hangs when
+	// reading credentials from docker-credential-osxkeychain.
+	// See issue https://github.com/docker/cli/issues/1862
+	mu sync.Mutex
 }
 
 func (ap *authProvider) Register(server *grpc.Server) {
 	auth.RegisterAuthServer(server, ap)
 }
 
 func (ap *authProvider) Credentials(ctx context.Context, req *auth.CredentialsRequest) (*auth.CredentialsResponse, error) {
+	ap.mu.Lock()
+	defer ap.mu.Unlock()
 	if req.Host == "registry-1.docker.io" {
 		req.Host = "https://index.docker.io/v1/"
 	}