Let's use a more concrete example. Let's say we write a Go program that copies a file. On Windows, this might use an API call like CopyFile:

https://msdn.microsoft.com/en-us/library/windows/desktop/aa3...

If you decompile the compiled Go program into C, it'd still have the references to API calls like this. These APIs would have to be implemented on the new OS for the decompiled program to work without modification.