in src/Google.Cloud.Functions.Hosting/HostingInternals.cs [153:158]
internal static Type? TryGetFunctionTarget(IConfiguration configuration, Assembly assembly)
{
var options = FunctionsFrameworkOptions.FromConfiguration(configuration);
string? target = options.FunctionTarget;
return target is null ? TryFindDefaultFunctionType(assembly.GetTypes()) : assembly.GetType(target);
}