use netcoreapp2.1 for testing
diff --git a/csharp/buildall.sh b/csharp/buildall.sh
index 50d8906..43b5ac3 100755
--- a/csharp/buildall.sh
+++ b/csharp/buildall.sh
@@ -10,8 +10,8 @@
dotnet build -c $CONFIG $SRC/Google.Protobuf.sln
echo Running tests.
-# Only test netcoreapp1.0, which uses the .NET Core runtime.
+# Only test netcoreapp2.1, which uses the .NET Core runtime.
# If we want to test the .NET 4.5 version separately, we could
# run Mono explicitly. However, we don't have any differences between
-# the .NET 4.5 and netstandard1.0 assemblies.
-dotnet test -c $CONFIG -f netcoreapp1.0 $SRC/Google.Protobuf.Test/Google.Protobuf.Test.csproj
+# the .NET 4.5 and netstandard2.1 assemblies.
+dotnet test -c $CONFIG -f netcoreapp2.1 $SRC/Google.Protobuf.Test/Google.Protobuf.Test.csproj