test: modify test-debugger-custom-port.js to use async-await

test/sequential/test-debugger-custom-port.js

@@ -1,4 +1,4 @@
-'use strict';
+use strict';
 const common = require('../common');
 
 common.skipIfInspectorDisabled();
@@ -9,22 +9,21 @@ const startCLI = require('../common/debugger');
 const assert = require('assert');
 
 // Custom port.
-{
-  const script = fixtures.path('debugger', 'three-lines.js');
+const script = fixtures.path('debugger', 'three-lines.js');
 
-  const cli = startCLI([`--port=${common.PORT}`, script]);
-
-  cli.waitForInitialBreak()
-    .then(() => cli.waitForPrompt())
-    .then(() => {
-      assert.match(cli.output, /debug>/, 'prints a prompt');
-      assert.match(
-        cli.output,
-        new RegExp(`< Debugger listening on [^\n]*${common.PORT}`),
-        'forwards child output');
-    })
-    .then(() => cli.quit())
-    .then((code) => {
-      assert.strictEqual(code, 0);
-    });
-}
+const cli = startCLI([`--port=${common.PORT}`, script]);
+(async function() {
+  try
+  {
+    await cli.waitForInitialBreak();
+    await cli.waitForPrompt();
+    assert.match(cli.output, /debug>/, 'prints a prompt');
+    assert.match(
+       cli.output,
+       new RegExp(`< Debugger listening on [^\n]*${common.PORT}`),
+       'forwards child output');
+  } finally {
+    const code = await cli.quit();
+    assert.strictEqual(code, 0);
+  }
+})();