public class DockerContext: DbContext
    {
        private bool InDocker { get { return Environment.GetEnvironmentVariable("DOTNET_RUNNING_IN_CONTAINER") == "true"; } }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!InDocker)
            {
// Здесь переопределяем ConnectionString для миграций
            }
        }

public static bool InDocker { get { return Environment.GetEnvironmentVariable("DOTNET_RUNNING_IN_CONTAINER") == "true"; } }
public static void Main(string[] args)
{
  var builder = WebApplication.CreateBuilder(args);
  builder.Services.AddDbContext<DockerContext>(options =>
                options.UseSqlServer(builder.Configuration.GetConnectionString(InDocker ? "DockerContext" : "MigrationContext") ?? throw new InvalidOperationException("Connection string 'DockerContext' not found.")));
}