Laravel 6.0 cannot be installed

[gaohw333]

Problem 1
- Installation request for schedula/laravel-passport-socialite ^2.0 -> satisfiable by schedula/laravel-passport-socialite[v2.0.0].
- Conclusion: remove laravel/framework v6.0.4
- Conclusion: don't install laravel/framework v6.0.4
- schedula/laravel-passport-socialite v2.0.0 requires illuminate/support ~5.7 -> satisfiable by illuminate/support[5.7.17, 5.7.18, 5.7.19, 5.7.x-dev, 5.8.x-dev, v5.7.0, v5.7.1, v5.7.10, v5.7.11, v5.7.15, v5.7.2, v5.7.20, v5.7.21, v5.7.22, v5.7.23, v5.7.26, v5.7.27, v5.7.28, v5.7.3, v5.7.4, v5.7.5, v5.7.6, v5.7.7, v5.7.8, v5.7.9, v5.8.0, v5.8.11, v5.8.12, v5.8.14, v5.8.15, v5.8.17, v5.8.18, v5.8.19, v5.8.2, v5.8.20, v5.8.22, v5.8.24, v5.8.27, v5.8.28, v5.8.29, v5.8.3, v5.8.30, v5.8.31, v5.8.32, v5.8.33, v5.8.34, v5.8.35, v5.8.36, v5.8.4, v5.8.8, v5.8.9].