Swoole releases 6.0.0 causes composer error

[gustavomazzafc]

Hi, recently Swoole release a new version, now, cause an error in composer to install this lib(depends on 5.0), anyone can help us?

[Jeckerson]

Related to this issue: shivammathur/setup-php#896

Update runs-on to more recent Ubuntu's version.

[elcreator]

#9