为什么程序包日志实例无法与Golang中的另一个程序包共享

Question

My project has some packages, I don't want to pass log instance from one function to another, instead use a global log instance in there packages.

Here is the demo I have done, but run go run main.go, nothing print in logs/replica.log.

What's wrong with my code?

├── log
│   └── replica.log
├── logs
│   └── logs.go
├── main.go



$ cat main.go

package main

import (
    "./logs"
)

func main() {
    logs.Debug("hello")
}

$ cat logs/logs.go

package logs

import (
    logging "github.com/op/go-logging"
    "os"
)

var log = logging.MustGetLogger("replica")
var format = logging.MustStringFormatter(
    `%{time:2006-01-02 15:04:05} [%{level:.4s}] %{shortfile}: %{message}`,
)

func init() {
    f, err := os.OpenFile("log/replica.log", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
    if err != nil {
        panic(err)
    }
    defer f.Close()

    backend1 := logging.NewLogBackend(f, "", 0)
    backend1Formatter := logging.NewBackendFormatter(backend1, format)
    logging.SetBackend(backend1Formatter)
}

func Debug(args ...interface{}) {
    log.Debug(args)
}

Answer 1

Yes, the defer in logs/logs.go:init() is the issue. Why is that the issue? Let's take a look at the Go Language Spec, specifically the section on Defer statements:

A "defer" statement invokes a function whose execution is deferred to the moment the surrounding function [...] reache[s] the end of its function body [...].

The file is closed when the end of the init function body is reached. Keep in mind, there's no good way to gracefully close a global file.