Flaska: If http server supports listenAsync (service-core for example) then use that instead of callback listen()

flaska.mjs

@@ -1066,6 +1066,10 @@ ctx.state.nonce = nonce;
     this.compile()
     this.server = this.http.createServer(this.requestStart.bind(this))
 
+    if (this.server.listenAsync && typeof(this.server.listenAsync) === 'function') {
+      return this.server.listenAsync(port, ip)
+    }
+
     return new Promise((res, rej) => {
       this.server.listen(port, ip, function(err) {
         if (err) return rej(err)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "flaska",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "Flaska is a micro web-framework for node. It is designed to be fast, simple and lightweight, and is distributed as a single file module with no dependencies.",
   "main": "flaska.mjs",
   "scripts": {

test/flaska.api.test.mjs

@@ -925,7 +925,7 @@ t.describe('#listenAsync()', function() {
     assert.strictEqual(checkIp, assertIp)
   })
 
-  t.test('call http correctly if only port specified', async function() {
+  t.test('call http and listen correctly if only port specified', async function() {
     const assertPort = 325897235
     let checkPort = null
     let checkIp = null
@@ -945,6 +945,53 @@ t.describe('#listenAsync()', function() {
     assert.strictEqual(checkPort, assertPort)
     assert.strictEqual(checkIp, '::')
   })
+  
+  t.test('call http and listenAsync correctly if supported', async function() {
+    const assertPort = 4632
+    const assertIp = 'asdf'
+    const assertReturns = { a: 1 }
+    const stubListenAsync = stub().resolves(assertReturns)
+
+    let flaska = new Flaska({}, {
+      createServer: function() {
+        return {
+          listenAsync: stubListenAsync,
+        }
+      }
+    })
+    assert.ok(flaska.requestStart)
+    flaska.requestStart = function() {
+      checkInternalThis = this
+      checkIsTrue = true
+    }
+    let res = await flaska.listenAsync(assertPort, assertIp)
+    assert.strictEqual(res, assertReturns)
+    assert.strictEqual(stubListenAsync.firstCall[0], assertPort)
+    assert.strictEqual(stubListenAsync.firstCall[1], assertIp)
+  })
+  
+  t.test('call http and listenAsync correctly if supported and ip is null', async function() {
+    const assertPort = 325897235
+    const assertReturns = { a: 1 }
+    const stubListenAsync = stub().resolves(assertReturns)
+
+    let flaska = new Flaska({}, {
+      createServer: function() {
+        return {
+          listenAsync: stubListenAsync,
+        }
+      }
+    })
+    assert.ok(flaska.requestStart)
+    flaska.requestStart = function() {
+      checkInternalThis = this
+      checkIsTrue = true
+    }
+    let res = await flaska.listenAsync(assertPort)
+    assert.strictEqual(res, assertReturns)
+    assert.strictEqual(stubListenAsync.firstCall[0], assertPort)
+    assert.strictEqual(stubListenAsync.firstCall[1], '::')
+  })
 
   t.test('register requestStart if no async', async function() {
     let checkIsTrue = false