我按照给出的说明这里安装 dotnet-sdk-2.2。运行最后一条命令时，出现以下错误：
$ sudo apt-get install dotnet-sdk-2.2
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
dotnet-sdk-2.2 : Depends: aspnetcore-runtime-2.2 (>= 2.2.1) but it is not going to be installed
Depends: dotnet-runtime-2.2 (>= 2.2.1) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
我正在运行 Ubuntu 18.10。