The filepath.Walk function takes a function callback. This is straight function with no context pointer. Surely a major use case for Walk is to walk a directory and take some action based on it, with reference to a wider context (e.g. entering each file into a table).
If I were writing this in C# I would use an object (with fields that could point back to the objects in the context) as a callback (with a given callback method) on it so the object can encapsulate the context that Walk is called from.
(EDIT: user "usr" suggests that the closure method occurs in C# too)
If I were writing this in C I'd ask for a function and a context pointer as a void * so the function has a context pointer that it can pass into the Walk function and get that passed through to the callback function.
But Go only has the function argument and no obvious context pointer argument.
(If I'd designed this function I would have taken an object as a callback rather than a function, conforming to the interface FileWalkerCallback or whatever, and put a callback(...) method on that interface. The consumer could then attach whatever context to the object before passing it to Walk.)
The only way I can think of doing it is by capturing the closure of the outer function in the callback function. Here is how I am using it:
func ScanAllFiles(location string, myStorageThing *StorageThing) (err error) {
numScanned = 0
// Wrap this up in this function's closure to capture the `corpus` binding.
var scan = func(path string, fileInfo os.FileInfo, inpErr error) (err error) {
numScanned ++
myStorageThing.DoSomething(path)
}
fmt.Println("Scan All")
err = filepath.Walk(location, scan)
fmt.Println("Total scanned", numScanned)
return
}