namespaces: Export env var and default value

Signed-off-by: Samuel Karp <skarp@amazon.com>

namespaces/context.go

@@ -8,8 +8,8 @@ import (
 )
 
 const (
-	namespaceEnvVar  = "CONTAINERD_NAMESPACE"
-	defaultNamespace = "default"
+	NamespaceEnvVar = "CONTAINERD_NAMESPACE"
+	Default         = "default"
 )
 
 var (
@@ -30,9 +30,9 @@ func WithNamespace(ctx context.Context, namespace string) context.Context {
 // NamespaceFromEnv uses the namespace defined in CONTAINERD_NAMESPACE or
 // default
 func NamespaceFromEnv(ctx context.Context) context.Context {
-	namespace := os.Getenv(namespaceEnvVar)
+	namespace := os.Getenv(NamespaceEnvVar)
 	if namespace == "" {
-		namespace = defaultNamespace
+		namespace = Default
 	}
 	return WithNamespace(ctx, namespace)
 }

namespaces/context_test.go

@@ -31,8 +31,8 @@ func TestContext(t *testing.T) {
 }
 
 func TestNamespaceFromEnv(t *testing.T) {
-	oldenv := os.Getenv(namespaceEnvVar)
-	defer os.Setenv(namespaceEnvVar, oldenv) // restore old env var
+	oldenv := os.Getenv(NamespaceEnvVar)
+	defer os.Setenv(NamespaceEnvVar, oldenv) // restore old env var
 
 	ctx := context.Background()
 	namespace, ok := Namespace(ctx)
@@ -45,7 +45,7 @@ func TestNamespaceFromEnv(t *testing.T) {
 	}
 
 	expected := "test-namespace"
-	os.Setenv(namespaceEnvVar, expected)
+	os.Setenv(NamespaceEnvVar, expected)
 	nctx := NamespaceFromEnv(ctx)
 
 	namespace, ok = Namespace(nctx)