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 -> nilslices -> nilmaps -> nilchannels -> nilfunctions -> nilinterfaces -> nil