How to set NuGet environment variable NUGET_CERT_REVOCATION_MODE` to false on appcenter.ms

I am working on Xamarin.Forms app that is using a private NuGet feed.

For iOS building, I use appcenter.ms that is recommended by Microsoft. I have set up the NuGet restore step via API key by adding Nuget.config next to .sln file.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
    <add key="DevOps" value="https://xxx.pkgs.visualstudio.com/_packaging/xxx/nuget/v3/index.json" />
  </packageSources>
<apikeys>
    <add key="https://xxx.pkgs.visualstudio.com/_packaging/xxx/nuget/v3/index.json" value="%encrypted_api_key%" />
</apikeys>
</configuration>

However, nuget restore on appcenter.ms takes so long that build times-out after 30 minutes.

I suspect that issue is the Revocation check mode

I would need to set the NUGET_CERT_REVOCATION_MODE to false.

How to set NuGet environment variable NUGET_CERT_REVOCATION_MODE to false on appcenter.ms? or disable it some other way?