How to access platform specific package documentation?

Question

We can access Go's package documentation online on the official website:

https://golang.org/pkg/

This only contains the package documentation available on the linux platform (GOOS), amd64 archicture (GOARCH).

Or offline via the go doc command, e.g package doc of the syscall package.

go doc syscall

This shows documentation for the platform of the Go SDK.

Some packages have different API based on the platform we target, most famous is the syscall package.

How can we access platform specific package documentation online and offline?

Answer 1

1. Online

Online, platform specific documentation can be accessed on the official Go home page, by appending the GOOS and GOARCH query parameters, similar to the environment variables.

For example, to access the syscall package documentation for Windows 64-bit platform, visit:

https://golang.org/pkg/syscall/?GOOS=windows&GOACH=amd64

To quickly verify that it works, search for the type DLL phrase (or simply DLL), as those don't appear on linux's syscall package.

2. Offline

The go tool has default target platform and architecture which can be overridden with the GOOS and GOARCH environment variables. So by default go doc syscall will show package documentation for the default platform and architecture.

To get doc for other platforms and / or architectures, all we need to do is change those environment variables.

On unix systems (e.g. linux, OS-X), we can simply prepend the go doc command with the new platform / architecture we're interested in, e.g. package doc of syscall for Windows (executed on Linux):

GOOS=windows go doc syscall

And that's all it takes. To quickly check if it works, print the DLL type and its methods:

GOOS=windows go doc syscall DLL

Example output:

type DLL struct {
    Name   string
    Handle Handle
}
    A DLL implements access to a single DLL.


func MustLoadDLL(name string) *DLL
func (d *DLL) FindProc(name string) (proc *Proc, err error)
func (d *DLL) MustFindProc(name string) *Proc
func (d *DLL) Release() (err error)

This is documented in the syscall package:

The details vary depending on the underlying system, and by default, godoc will display the syscall documentation for the current system. If you want godoc to display syscall documentation for another system, set $GOOS and $GOARCH to the desired system. For example, if you want to view documentation for freebsd/arm on linux/amd64, set $GOOS to freebsd and $GOARCH to arm.