标准库log
1.自定义log前缀
log.SetPrefix()
log.SetFlags()
2.log.Fatalf()
log.Fatalf("Site is down: %v\n",err)
3.log.Printf()
log.Printf("ping failed:%v;networking disabled",err)
4.log.Fprintf()
直接输出到标准错误流中
log.Fprintf(os.Stderr,"ping failed: %v;networking disable\n",err)