Go语言的“main package”
以下摘自The Go Programming Language：
Package main is special. It defines a standalone executable program, not a library. Within package main the function main is also special—it’s where execution of the program begins. Whatever main does is what the program does.
main package不同于其它library package，它定义了一个可执行程序。其中的main函数即是可执行文件的入口函数。