The build failed. Fix the build errors and run again
git clone https://github.com/grpc/grpc-dotnet.git
cd grpc-dotnet/examples/Racer/Server
$ dotnet run
warn: Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServer[8]
The ASP.NET Core developer certificate is not trusted. For information about trusting the ASP.NET Core developer certificate, see https://aka.ms/aspnet/https-trust-dev-cert.
info: Microsoft.Hosting.Lifetime[14]
Now listening on: https://localhost:5001
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
Content root path: /home/burak/Desktop/grpc/grpc-dotnet/examples/Racer/Server
^Cinfo: Microsoft.Hosting.Lifetime[0]
Application is shutting down...
Attempting to cancel the build...
^C
^C
^C
#Then when I run it again that command doesn't work.
$ dotnet run
The build failed. Fix the build errors and run again.
Linux Mint 20.2 Cinnamon
dotnet --info
.NET SDK:
Version: 7.0.100-rc.1.22431.12
Commit: f1cf61e1c0
Runtime Environment:
OS Name: linuxmint
OS Version: 20.2
OS Platform: Linux
RID: linux-x64
Base Path: /usr/share/dotnet/sdk/7.0.100-rc.1.22431.12/
Host:
Version: 7.0.0-rc.1.22426.10
Architecture: x64
Commit: 06aceb7015
.NET SDKs installed:
3.1.423 [/usr/share/dotnet/sdk]
7.0.100-rc.1.22431.12 [/usr/share/dotnet/sdk]
.NET runtimes installed:
Microsoft.AspNetCore.App 3.1.29 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.0-rc.1.22427.2 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.29 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.0-rc.1.22426.10 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Other architectures found:
None
Environment variables:
Not set
global.json file:
/home/burak/Desktop/grpc/grpc-dotnet/global.json
Learn more:
https://aka.ms/dotnet/info
Download .NET:
https://aka.ms/dotnet/download
I can't reproduce this:

There is nothing unusual about that app. It's a standard Kestrel server. I'm not sure what could cause the build to fail. Your error message says the build failed because or errors. What are those errors? Is there a process in use?
I'm not using any third-party project. Just want to run those examples but when I run the racer example I'm getting that error. Before this, I was not getting such an error. After restart to my pc, I can run without racer and mailer other examples like Counter/Greeter, etc.
I can't find out anymore if I don't have the build errors.
.NET SDK:
Version: 7.0.100-rc.1.22431.12
Actually, I didn't have any problem until running these examples. But it seems looks like the problem is .net SDK
https://github.com/dotnet/sdk/issues/28471
Triage: Closing this issue as you believe it's an issue in the SDK.