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I'm supposed to be done with my contract by the end of August, but this opportunity has been incredible for me and I don't mind working for him without getting paid since there are so many opportunities in the place I work.

I'm working as a software engineer and I am also doing research, which at the end will result in me having my name published in a paper. I would like to continue my scientific journey with this research facility because I think it's a great environment to learn. I'm not looking to get re-hired and make the same amount/more money than I am now. I won't be working full-time if I want to work for free because I also have my PhD program. I would like to get a great recommendation for future jobs I'm applying for and I would like to have more opportunities to participate in research that will get me published in more papers.

Trivial: I'm a girl, since everyone is assuming I'm not.

How can I ask him this?

I'm supposed to be done with my contract by the end of August, but this opportunity has been incredible for me and I don't mind working for him without getting paid since there are so many opportunities in the place I work.

I'm working as a software engineer and I am also doing research, which at the end will result in me having my name published in a paper. I would like to continue my scientific journey with this research facility because I think it's a great environment to learn. I'm not looking to get re-hired and make the same amount/more money than I am now. I won't be working full-time if I want to work for free because I also have my PhD program. I would like to get a great recommendation for future jobs I'm applying for and I would like to have more opportunities to participate in research that will get me published in more papers.

How can I ask him this?

Trivial: I'm a girl, since everyone is assuming I'm not.

Edit:

The question is: How can I ask my boss if I can stay on a project for free, after my contract is up?

My question is not: Should I work for free or not? or: Is it legal for me to work for free?

I'm supposed to be done with my contract by the end of August, but this opportunity has been incredible for me and I don't mind working for him without getting paid since there are so many opportunities in the place I work.

How can I ask him this?

I'm supposed to be done with my contract by the end of August, but this opportunity has been incredible for me and I don't mind working for him without getting paid since there are so many opportunities in the place I work.

I'm working as a software engineer and I am also doing research, which at the end will result in me having my name published in a paper. I would like to continue my scientific journey with this research facility because I think it's a great environment to learn. I'm not looking to get re-hired and make the same amount/more money than I am now. I won't be working full-time if I want to work for free because I also have my PhD program. I would like to get a great recommendation for future jobs I'm applying for and I would like to have more opportunities to participate in research that will get me published in more papers.

Trivial: I'm a girl, since everyone is assuming I'm not.

How can I ask him this?

I'm supposed to be one with my contract by the end of August but this opportunity has been incredible for me and I don't mind working for him without getting paid since there are so many opportunities in the place I work. How can I ask him this?

I'm supposed to be done with my contract by the end of August, but this opportunity has been incredible for me and I don't mind working for him without getting paid since there are so many opportunities in the place I work. 

How can I ask him this?