* chore: fix some errors detected by staticcheck
* feat: remove `rand.Seed()` usage for possibly using "fastrand64" runtime to avoid locking
ref: https://pkg.go.dev/math/rand#Seed
* Added test for no terminate signal
* unified drain support for vmess and shadowsockets
* drain: add generated file
Co-authored-by: Shelikhoo <xiaokangwang@outlook.com>