ctx.cs

public Class1
{
  public Class1(DbContextOptions<MyContext> options) : base(options)
  {
    if (configuration["Env"] == "Cloud")
    {
      var conn = (Microsoft.Data.SqlClient.SqlConnection)Database.GetDbConnection();
      conn.AccessToken = (new Microsoft.Azure.Services.AppAuthentication.AzureServiceTokenProvider()).GetAccessTokenAsync("https://database.windows.net/").Result;
    }

    Database.EnsureCreated();
  }
}