os.sleep is not working properly

**info:**
- nim compiler version: `1.4.8`
- inim version : 0.6.1
- os: windows 10

**the code:**
```
import os

nim> proc uuu=   
     echo "start"
     sleep 1000
     echo "end"

nim> uuu()
```

**result:**
    it prints "end" immediately after printing "start"

**expected behavior:**
    it should sleep for 1s and then print "end" 