Oils/ stain for a drinking mug

I was thinking about making a coffee drinking mug out of wood but i dont know how to seal the wood. Could i try to seal it with walnut oil? I really wanted to stain the outside of the wood with coffee but i still need to seal the inside of the mug somehow. This is a very new process to me and i dont want to have bacteria growing in the mug.

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Ron here...

Once you stain the outside treat the whole mug with walnut oil.

A few coats. Let dry well in between.