Fix GitHub Actions build error: Update .NET version to support C# 11

[Copilot]

Problem

GitHub Actions builds were failing with the error:

CSC : error CS1617: Invalid option '11' for /langversion. Use '/langversion:?' to list supported values.

Root Cause

The project specifies <LangVersion>11</LangVersion> (C# 11) in the .csproj file, but the GitHub Actions workflows were configured to use .NET 6.0.x, which only supports up to C# 10. C# 11 language features were introduced with .NET 7.0.

Solution

Updated both GitHub Actions workflows to use .NET 7.0.x instead of .NET 6.0.x:

• .github/workflows/dotnet.yml
• .github/workflows/release.yml

Technical Details

The codebase legitimately uses C# 11 features, specifically the scoped keyword for performance optimization with ref structs:

private void FormatInternal(scoped ref CharBuffer buffer, int value)
private void Format(scoped ref CharBuffer buffer, long value, bool fillMil = false)

Rather than downgrading the language features and losing performance benefits, updating the CI environment to support C# 11 is the appropriate solution.

Compatibility

This change maintains full backward compatibility:

• The compiled library still targets net6.0;netstandard2.0;netstandard2.1 runtimes
• Only the build-time environment was updated to support C# 11 compilation
• No functional code changes were required

Fixes #16.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.