判断是否为debug模式,是就写入下面这一段日志到系统标准输出
[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
- using env: export GIN_MODE=release
- using code: gin.SetMode(gin.ReleaseMode)
之后就接着创建框架的实例对象gin.go -> Engine struct,初始化后将该实例的指针返回.