// LoggerミドルウェアをJSON形式で
e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
    Format: `{"time":"${time_rfc3339}","method":"${method}","uri":"${uri}","status":${status},"latency_ms":${latency_ms},"remote_ip":"${remote_ip}","error":"${error}"}` + "\n",
}))

// LoggerミドルウェアをLTSV形式で
e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
    Format: "time:${time_rfc3339}\tmethod:${method}\turi:${uri}\tstatus:${status}\tlatency_ms:${latency_ms}\tremote_ip:${remote_ip}\terror:${error}\n",
}))