[Bug]: Canceling msbuild restore is slow when invalid/unreachable source configured

[zivkan]

NuGet Product Used

MSBuild.exe

Product Version

msbuild 17.2

Worked before?

No response

Impact

It bothers me. A fix would be nice

Repro Steps & Context

1. Find a solution that does not restore quickly. The longer it takes, the better. For example, try https://github.com/OrchardCMS/OrchardCore
2. Run dotnet nuget add source https://invalid.nuget.org/v1234/index.json -n invalidSource
3. Run msbuild -t:restore -v:m
4. Wait for "error NU1301: Unable to load the service index for source ..." messages start appearing
5. Press ctrl+C
6. See that "Attempting to cancel the build" appears immediately, but it can take seconds, or minutes, for the command prompt to return (restore to end), during which time a bunch more NU1301 errors will be reported.

By comparison, if you press ctrl-c quickly after the "Determining projects to restore" message is displayed, the command line returns immeidately. Similarly, when using -p:RestoreUseStaticGraphEvaluation=true, ctrl-c also exits immediately.

Verbose Logs

No response