Laravel Composer could not install tymon/jwt-auth

 Problem 1
    - Root composer.json requires tymon/jwt-auth ^0.5.12 -> satisfiable by tymon/jwt-auth[0.5.12].
    - tymon/jwt-auth 0.5.12 requires illuminate/support ~5.0 -> found illuminate/support[v5.0.0, ..., 5.8.x-dev] but these were not loaded, likely because it conflicts with another require.

使用如下方式：

composer require tymon/jwt-auth --ignore-platform-reqs