How to reliably detect os/platform in Go

Here's what I'm currently using, which I think gets the job done, but there's got to be a better way:

func isWindows() bool {
    return os.PathSeparator == '\\' && os.PathListSeparator == ';'
}

As you can see, in my case all I need to know is how to detect windows but I'd like to know the way to detect any platform/os.

Play:

http://play.golang.org/p/r4lYWDJDxL

Detection at compile time

If you're doing this to have different implementations depending on the OS, it is more useful to
have separate files with the implementation of that feature and add build tags to each
of the files. This is used in many places in the standard library, for example in the os package.

These so-called "Build constraints" or "Build tags" are explained here.

Say you have the constant PATH_SEPARATOR and you want that platform-dependent, you
would make two files, one for Windows and one for the (UNIX) rest:

/project/path_windows.go
/project/path_unix.go

The code of these files would then be:
path_windows.go

// +build windows

package project

const PATH_SEPARATOR = '\\'

path_unix.go

// +build !windows

package project

const PATH_SEPARATOR = '/'

You can now access PATH_SEPARATOR in your code and have it platform dependant.
Detection at runtime

If you want to determine the operating system at runtime, use the runtime.GOOS
variable:

if runtime.GOOS == "windows" {
    fmt.Println("Hello from Windows")
}

While this is compiled into the runtime and therefore ignores the environment,
you can nevertheless be relatively certain that the value is correct.
The reason for this is that every platform that is worth distinguishing needs
rebuilding due to different executable formats and thus has a new GOOS value.

Stack Overflow Q#19847594, score: 218