Update main.go

[chensanle]

---

name: Pull request
about: Possible panic caused by type conversion
title: ''
labels: ''
assignees: ''

1. Are you opening this pull request for bug-fixs, optimizations or new feature?

2. Please describe how these code changes achieve your intention.

3. Please link to the relevant issues (if any).

4. Which documentation changes (if any) need to be made/updated because of this PR?

4. Checklist

• I have squashed all insignificant commits.
• I have commented my code for explaining package types, values, functions, and non-obvious lines.
• I have written unit tests and verified that all tests passes (if needed).
• I have documented feature info on the README (only when this PR is adding a new feature).
• (optional) I am willing to help maintain this change if there are issues with it later.