Security upgrade alpine from 3.12 to 3.14

[cloudgeek7]

Changes included in this PR nginx-golang-mysql/backend/Dockerfile I recommend upgrading to alpine:3.14, as this image has only 0 known vulnerabilities. To do this, merge this pull request, then verify your application still works as expected.

Some of the most important vulnerabilities in your base image include:

Severity Priority Score / 1000 Issue Exploit Maturity high severity 400 Improper Handling of Exceptional Conditions SNYK-ALPINE312-BUSYBOX-1089799 No Known Exploit high severity 400 Improper Handling of Exceptional Conditions SNYK-ALPINE312-BUSYBOX-1089799 No Known Exploit

[glours]

Hello @cloudgeek7 Thanks for all your security PRs, to be able to merge them I just need you sign your commits You can follow this simple instructions