migrate to "export default"

also, set no-use-before-define in linter

src/sftp.js

@@ -4,7 +4,7 @@ import blobs from './blobs.js';
 import BoxError from './boxerror.js';
 import constants from './constants.js';
 import debugModule from 'debug';
-import * as docker from './docker.js';
+import docker from './docker.js';
 import hat from './hat.js';
 import infra from './infra_version.js';
 import mounts from './mounts.js';
@@ -13,17 +13,13 @@ import paths from './paths.js';
 import safe from 'safetydance';
 import services from './services.js';
 import shellModule from './shell.js';
-import * as volumes from './volumes.js';
+import volumes from './volumes.js';
 
 const debug = debugModule('box:sftp');
 const shell = shellModule('sftp');
 
 const DEFAULT_MEMORY_LIMIT = 256 * 1024 * 1024;
 
-export {
-    start,
-    DEFAULT_MEMORY_LIMIT,
-};
 
 async function ensureKeys() {
     for (const keyType of [ 'rsa', 'ed25519' ]) {
@@ -131,3 +127,8 @@ async function start(existingInfra) {
 
     if (existingInfra.version !== 'none' && existingInfra.images.sftp !== image) await docker.deleteImage(existingInfra.images.sftp);
 }
+
+export default {
+    start,
+    DEFAULT_MEMORY_LIMIT,
+};