TryLock in stdlib

[AlekSi]

TryLock was added in stdlib: https://github.com/golang/go/commit/645d07819b2224ba4d759829443f7c6442162c69

I think this library should use a type alias for sync.Mutex in Go 1.18:

//go:build go1.18
// +build go1.18

type Mutex = sync.Mutex