laravel 5.4 composer 失败

[NominationP]

我用的环境

PHP 版本：5.6 (用的docker里面是7.0)
overtrue/wechat 版本：4.0
laravel 5.4

问题及现象

composer require "overtrue/wechat:~4.0" -vvv

描述你的问题现象，报错贴截图粘贴或者贴具体信息，提供必要的代码段

Reading /Users/yibo/.composer/cache/repo/https---packagist.org/provider-kodova$hamcrest-php.json from cache
Resolving dependencies through SAT
Dependency resolution completed in 0.117 seconds
Reading /Users/yibo/.composer/cache/repo/https---packagist.org/provider-overtrue$wechat.json from cache
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - The requested package overtrue/wechat ~4.0 is satisfiable by overtrue/wechat[4.0.0-alpha.2, 4.0.0-alpha1, 4.0.0-beta.1] but these conflict with your requirements or minimum-stability.


Installation failed, reverting ./composer.json to its original content.

[overtrue]

4.0 还没有发布。。。