Upgrade to go 1.21, fix #300

[Almenon]

Pull Request

Related Github Issues

• tests fail when run in VSCode in Windows #300

Description

I confirmed the Build and test code workflow is passing with the following changes

• Upgrade to go 1.21. Ideally we would support 1.20 too, but there was some weird issue where Github CI would run 1.21 even if I specified '1.20'. Supporting older go versions is not that important because the project compiles to an executable, so I decided to just drop 1.20 support.
• Upgrade certain Github actions
• Fix tests fail when run in VSCode in Windows #300
• Add personal vscode workspace files to gitignore
• removed actions/cache@v2 - latest go action has builtin cache
• Run go mod tidy

Security Implications

• No longer supporting go versions that are end-of-life for security support 🚀 https://endoflife.date/go

System Availability

• [none]

[Almenon]

Closing, will re-open with fixed conflicts