[ubuntu, windows] GOROOT environment variable will be removed on March, 1

[AlenaSviridenko]

Breaking changes
Predefined GOROOT environment variable will be removed on March, 1 from all Ubuntu and Windows images

Target date
Images deployment will start on March, 1 and will take 3-4 days.

The motivation for the changes

The GOROOT environment variable is mostly deprecated, and no setup requires it. The problem with hardcoding a GOROOT is that if any other go tool is in use (for example, because one compiled Go tip), the environment variable will override its autodetected GOROOT.

Please, see more details in #2655

Possible impact
If your workflow directly use GOROOT — your build will be broken.

Virtual environments affected

• Ubuntu 16.04
• Ubuntu 18.04
• Ubuntu 20.04
• macOS 10.13
• macOS 10.14
• macOS 10.15
• macOS 11.0
• Windows Server 2016 R2
• Windows Server 2019

Mitigation ways
Set environment variable as
echo "GOROOT=$GOROOT_1_15_X64" >> $GITHUB_ENV

[miketimofeev]

We've finished image deployments!