egg-mysql : Duplicate entry '137' for key 'PRIMARY'
## What happens?
doc says can update data with id in it, but in fact when do like this it throw Duplicate entry '137' for key 'PRIMARY' errors
i did exactly as below
![image](https://user-images.githubusercontent.com/11257690/93550263-9d274680-f99d-11ea-8147-c6075d7b30ff.png)

## Mini Showcase Repository(REQUIRED)
> Provide a mini GitHub repository which can reproduce the issue.
> Use `npm init egg --type=simple bug` then upload to your GitHub

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## How To Reproduce

**Steps to reproduce the behavior:**
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**Expected behavior**
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## Context
- **Node Version**:
- **Egg Version**:
- **Plugin Name**:
- **Plugin Version**:
- **Platform**:

![image](https://user-images.githubusercontent.com/11257690/93550137-60f3e600-f99d-11ea-9807-a4fb3ecf04e4.png)

