How to build binary in package in Golang?

Question

I have a project in github.com/user called project:

src/
    github.com/user/project
        sub1/
            main.go
            sub1.exe (??)
        sub2/
            main.go
            sub2.exe (??)

I am trying to compile the package in my project. When I:

$ cd github.com/user/project/sub1
$ go build

Nothing happens. go build seems to finish without complaining, but there is no executable file. How can I build packages into executable?

"go version go1.3 windows/amd64"

If main.go has a main() function, it should build the executable and call it sub1.exe in Windows. Isn't sub1.exe what you are looking for? Remove it and run go build again to see if it is created. — siritinga
– siritinga, Commented Feb 8, 2015 at 17:01
Hm, there is no executable. I am in the directory of the package. I am using Windows, but building from cygwin commandline. But even when using Windows cmd, there is no executable. — Kiril
– Kiril, Commented Feb 9, 2015 at 6:38

Volker · Accepted Answer · 2015-02-09 00:11:06Z

11

It doesn't matter if you name your file main.go or shubudoo.go. The only thing what matters if you want to build an executable (a command) is that your files start with package main. One more thing: Go has absolutely no notion of "subpackage": All packages are equal for the compiler. The filesystem nesting is for your convenience only.

answered Feb 9, 2015 at 0:11

Volker

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5 Comments

Kiril Over a year ago

So, it's not possible to have a main() in a package other than main?

Kiril Over a year ago

The link is what I meant. It's a new main package in a project.

Volker Over a year ago

I have to admit I do not understand your question. Any package which is declared package main must have a main() function and the go tool will build such a package into an executable and the main() function will be called when you run the executable. Regarding camget: camget is such a package main package and it contains a main() function an it is built into an executable. It does not matter if other packages, other non-main-packages, completely unrelated stuff to Go or whatever lives in other directories (higher up, siblings or subfolders).

Kiril Over a year ago

My misunderstanding was, that I thought I could build packages into executable binaries, if the packages provided a main(), regardless of whether the package is main or cmd or xxx. I thought the main() decided whether there is an executable.

Volker Over a year ago

No, it is package main and func main() { for an executable.

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