Optimize the godoc and examples code

- Robotgo version (or commit ref):
- Go version:
- Gcc version:
- Operating system and bit:
- Resolution:
- Can you reproduce the bug at [Examples](https://github.com/go-vgo/robotgo/blob/master/examples/main.go):
  - [ ] Yes (provide example code)
  - [ ] No
  - [ ] Not relevant
- Provide example code:

```Go

```
- Log gist:

## Description

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