title: Go configurable logger with file logging possibility
body: <p>I'm looking for logging library in Go, something similar like log4j in java.</p>
  
  <ol>
  <li><p>As I understood build-in logger from 'log' package have restricted possibility in configurations and log levels.</p></li>
  <li><p>Maybe someone used one of <a href="https://godoc.org/github.com/op/go-logging" rel="nofollow">https://godoc.org/github.com/op/go-logging</a>, <a href="https://github.com/cihub/seelog" rel="nofollow">https://github.com/cihub/seelog</a>?</p></li>
  <li><p>What about concurrency issues? What is the best way to store logger in system? One per program or create loggers every time?</p></li>
  </ol>
  
  <p>Thanks!</p>