go nil 是什么

一、介绍

nil是在go中的一个变量。
在源码 src/builtin/builtin.go

// nil is a predeclared identifier representing the zero value for a
// pointer, channel, func, interface, map, or slice type.
var nil Type // Type must be a pointer, channel, func, interface, map, or slice type

// Type is here for the purposes of documentation only. It is a stand-in
// for any Go type, but represents the same type for any given function
// invocation.
type Type int

nil是一个零值，

bool      -> false                              
numbers -> 0                                 
string    -> ""      

pointers -> nil
slices -> nil
maps -> nil
channels -> nil
functions -> nil
interfaces -> nil