## Logger (日志) 中間件
Logger 中間件記錄有關每個 HTTP 請求的信息。
*用法*
```go
e.Use(middleware.Logger())
```
*輸出樣例*
```json
{"time":"2017-01-12T08:58:07.372015644-08:00","remote_ip":"::1","host":"localhost:1323","method":"GET","uri":"/","status":200, "latency":14743,"latency_human":"14.743μs","bytes_in":0,"bytes_out":2}
```
### 自定義配置
*用法*
```go
e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
Format: "method=${method}, uri=${uri}, status=${status}\n",
}))
```
上面的示例使用 `Format` 來記錄請求方法和請求 URI 。
*輸出樣例*
```sh
method=GET, uri=/, status=200
```
### 配置
```go
LoggerConfig struct {
// Skipper 定義了一個跳過中間件的函數.
Skipper Skipper
// 日志的格式可以使用下面的標簽定義。:
//
// - time_unix
// - time_unix_nano
// - time_rfc3339
// - time_rfc3339_nano
// - id (Request ID - Not implemented)
// - remote_ip
// - uri
// - host
// - method
// - path
// - referer
// - user_agent
// - status
// - latency (In microseconds)
// - latency_human (Human readable)
// - bytes_in (Bytes received)
// - bytes_out (Bytes sent)
// - header:<name>
// - query:<name>
// - form:<name>
//
// 例如 "${remote_ip} ${status}"
//
// 可選。默認值是 DefaultLoggerConfig.Format.
Format string `json:"format"`
// Output 是記錄日志的位置。
// 可選。默認值是 os.Stdout.
Output io.Writer
}
```
*默認配置*
```go
DefaultLoggerConfig = LoggerConfig{
Skipper: defaultSkipper,
Format: `{"time":"${time_rfc3339_nano}","remote_ip":"${remote_ip}","host":"${host}",` +
`"method":"${method}","uri":"${uri}","status":${status}, "latency":${latency},` +
`"latency_human":"${latency_human}","bytes_in":${bytes_in},` +
`"bytes_out":${bytes_out}}` + "\n",
Output: os.Stdout
}
```
更多細節見：[golang echo 代碼詳解之 log 篇](https://laily.net/article/golang%20echo%20%e4%bb%a3%e7%a0%81%e8%af%a6%e8%a7%a3%e4%b9%8b%20log%20%e7%af%87)
