nil update

Author: ljq

EN/null-judge.md

@@ -15,6 +15,8 @@
 ### You cannot simply determine whether a struct is nil, because it can never be nil. You can determine whether it is empty by returning an error
 ### Common practice in golang standard library: if err! = nil
 
+### In the official document of go, nil is a predefined identifier, representing zero value of pointer, channel, function, interface, map or slice, not a reserved keyword of go
+### Nil can only be assigned to a variable of type pointer, channel, func, interface, map or slice (non base type) otherwise, panic will be raised
 
 ### usual type nil
 

zh_CN/null-judge.md

@@ -15,6 +15,9 @@
 ### 不能单纯地判断一个struct是不是nil，因为它永远不可能是nil，可以通过返回一个error来判断是否为空，
 ### golang标准库里的常见做法：if err != nil
 
+### Go官方文档中，nil是预定义的标识符，代表指针、通道、函数、接口、映射或切片的零值,非 GO 的保留关键字
+### nil只能赋值给指针、channel、func、interface、map或slice类型的变量 (非基础类型) 否则会引发 panic
+
 ### 常见类型的 nil
 
 ```