Bump up Go version to 1.18

What's Changed

• Devlights/issue508 by @devlights in #509
• Remove-ioutil-usage by @devlights in #510
• Add-html-template-example by @devlights in #511
• Add examples/singleapp/sigquit_like_javavm/main.go by @devlights in #512
• Add-fileio-performance-example by @devlights in #513
• Add sort examples by @devlights in #514
• Add-slice-performance-tips by @devlights in #515
• Add-strconv-examples by @devlights in #516
• Add-parseint-tips by @devlights in #517
• Add-strconv-examples by @devlights in #518
• Bumpup-go-version-118 by @devlights in #519
• Update-gomy-version by @devlights in #520

Full Changelog: v0.3.0...v0.4.0