我无法安装软件包System.Net.Http.WebRequest。救命！
$ dotnet add package System.Net.Http.WebRequest
Writing /tmp/tmp91vAjR.tmp
info : Adding PackageReference for package 'System.Net.Http.WebRequest' into project '/home/porton/Projects/ii/BravoDB/BravoDBDebug/BravoDBDebug.csproj'.
info : Restoring packages for /home/porton/Projects/ii/BravoDB/BravoDBDebug/BravoDBDebug.csproj...
info : GET https://api.nuget.org/v3-flatcontainer/system.net.http.webrequest/index.json
info : NotFound https://api.nuget.org/v3-flatcontainer/system.net.http.webrequest/index.json 1264ms
error: Unable to find package System.Net.Http.WebRequest. No packages exist with this id in source(s): nuget.org
error: Package 'System.Net.Http.WebRequest' is incompatible with 'all' frameworks in project '/home/porton/Projects/ii/BravoDB/BravoDBDebug/BravoDBDebug.csproj'.