gulp4.0 存在的錯誤信息 The following tasks did not complete: default,Did you forget to signal async completion?

當gulp為如下代碼的時候：

//  以下代碼會執行在node環境下
const gulp = require( "gulp" );

//  創建一個gulp的任務
gulp.task( "default",function(){
    console.log( "gulp default task" );
} );

運行結果：

The following tasks did not complete: default
Did you forget to signal async completion?

修改方法：

//  以下代碼會執行在node環境下
const gulp = require( "gulp" );

//  創建一個gulp的任務
gulp.task( "default",function(done){
    console.log( "gulp default task" );
    done();
} );