It's dialectal, most people don't talk like this or understand this type of talk. But there are some people who talk like this, we call them "hillbillies" in the US. They are countryside folks and may or may not have an extreme dialect.

It's a made-up variation of using 'gosh'. 'Gosh' is a softened, non-blasphemous version of God to show mild shock or surprise.

Thanks a lot!

It "was the dog-musher’s expression of astonishment".

“Gosh-swoggled” doesn’t mean anything, it’s a humorous word. It probably means he will be drunk or something, but it’s easier to tell with context.