Github user jeking3 commented on the issue:
https://github.com/apache/thrift/pull/1449
Currently the Ubuntu Xenial image which runs our cross tests in CI is
installing dotnet-sdk-2.0.3, as is our Ubuntu Artful image. The latest is
dotnet-sdk-2.1.4. Normally we like to have an older language level in the mix
somewhere; so if your changes work properly on 2.0.3 that's great; we should
update the artful Dockerfile to 2.1.4 in that case, so we have a "make check"
environment on the latest SDK.---
