Trying writes via go-routine (async writing, reopen and more). Unfortunately performance is worse than using locks.
benchmark:
BenchmarkAccessLog-8 534584 2177 ns/op 744 B/op 3 allocs/op
BenchmarkPlainFileWithLock-8 1000000 1223 ns/op 305 B/op 1 allocs/op
BenchmarkPlainFileWithoutLock-8 1000000 1797 ns/op 222 B/op 1 allocs/op