Travis-CI unable to find dotnet 8 sdk

Question

I'm using travis-ci.com to build repositories for Amazon Elastic Container Registry (ECR).

Inside of my .travis.yml file, I am trying to tell Travis to install the dotnet 8.0.203 sdk:

  language: csharp
  solution: src/RedisGeo.s1n
  services:
    - docker
  matrix:
    include:
      - os: linux
        dist: trusty
        sudo: required
        dotnet: 8.0.203
        mono: none
        env: DOTNETCORE=8

When I fire off a build, it fails with the following message:

      Installing .NET Core
    $ export DOTNET_SKIP_FIRST_TIME_EXPERIENCE=1
    $ export DOTNET_CLI_TELEMETRY_OPTOUT=1
    12.65s0.32sE: Unable to locate package dotnet-sdk-8.0
    E: Couldn't find any package by glob 'dotnet-sdk-8.0'
    E: Couldn't find any package by regex 'dotnet-sdk-8.0'
    The command "sudo apt-get install -qq dotnet-sdk-8.0=8.0.203*" failed and exited with 100 during .

The only example I found online were pointing to older versions of the dotnet sdk. I followed the pattern, but it still fails. What do I need to change in my .travis.yml file to tell Travis to download the dotnet sdk version 8.0.203 (or any version 8.0 and above)?

Thanks