Tigran

Please check my [PR](https://github.com/spf13/afero/pull/364) with fix. I can't use the library with this bug.

@bep hi, this is an old pull request for https://github.com/spf13/afero/issues/141 issue. I updated the branch and resolved conflicts. If you have time could you look at it please, it would...

@bep any comments or suggestions here please

@bep Thanks a lot. I just pushed it without merge commits. Could you please have a look?

@bep `unnecessary assignment` static check error fixed

@bep can we merge it please ?

@bep your attention is required. Could you please proceed with checks ?

@bep thank you so much :pray:

Actually [this merged PR](https://github.com/spf13/afero/pull/239) will not work. You need to update underlying `memdir` map as well. here is a case where you will get a panic: ```golang fs := NewMemMapFs()...

@bep Could you please have a look for this PR as well. It also related with https://github.com/spf13/afero/pull/364