./startup.sh: 21: Syntax error: word unexpected (expecting "in")

- [ ] I have searched the [issues](https://github.com/apache/dubbo-admin/issues) of this repository and believe that this is not a duplicate.
- [ ] I have checked the [REAMDE](https://github.com/apache/dubbo-admin/blob/develop/README.md) of this repository and believe that this is not a duplicate.

### Is your feature request related to a problem? Please describe.
ubuntu系统启动时报“./startup.sh: 21: Syntax error: word unexpected (expecting "in")”

: not foundh: 2:
./startup.sh: 21: Syntax error: word unexpected (expecting "in")

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### Describe alternatives you've considered
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### Additional context
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Start with startup.sh, especially line 21, and compare its shell syntax with the Ubuntu environment reported in the issue. Run ./startup.sh on Ubuntu to reproduce the error; done means the script starts without the reported syntax error.

Written by the indexing model from the issue text.