How professional is it for a guy to ask for a girls number on his job?

Like a coffee shop barrista, i am the girl who does find this guy intriguing. I just don't have the guts to ask... im a bit shy my friend thinks he has an interest in me but i know not to read too much into things cuz people can be just genuinely nice.
How professional is it for a guy to ask for a girls number on his job?
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