Nil Pointer Error

[mohnark]

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0xccf8cd]

goroutine 1 [running, locked to thread]:
main.getCategories()
tnris.org/bulk-downloader/bulk-downloader.go:385 +0xad
main.main()
tnris.org/bulk-downloader/bulk-downloader.go:193 +0x7a5