Golang func main() in packages other than main?

Question

In the case, for example, of helloworld, the name of the package is main and there is also a func main() statement. But I have also seen code which func main() which is in some other package. The code, however, seems like it might be used as a standalone program. So what does it mean to have a func main() with a package statement other than package main?

Answer 1

The Go programming language is defined by its specification.

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The Go Programming Language Specification

Program execution

A complete program is created by linking a single, unimported package called the main package with all the packages it imports, transitively. The main package must have package name main and declare a function main that takes no arguments and returns no value.

func main() { … }

Program execution begins by initializing the main package and then invoking the function main. When that function invocation returns, the program exits. It does not wait for other (non-main) goroutines to complete.

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The function name main has no special significance outside package main.