code: func (ctx *ProxyCtx) Logf(msg string, argv ...interface{}) {
  	if ctx.proxy.Verbose {
  		ctx.printf("INFO: "+msg, argv...)
  	}
  }
docs: // Logf prints a message to the proxy's log. Should be used in a ProxyHttpServer's filter
  // This message will be printed only if the Verbose field of the ProxyHttpServer is set to true
  //
  //	proxy.OnRequest().DoFunc(func(r *http.Request,ctx *goproxy.ProxyCtx) (*http.Request, *http.Response){
  //		nr := atomic.AddInt32(&counter,1)
  //		ctx.Printf("So far %d requests",nr)
  //		return r, nil
  //	})