SAML Request AssertionConsumerServiceURL is nil

Please i’m having issue getting the correcl saml request data to work using this library - Samly - Add SAML SSO to your Phoenix application (now with multiple identity provider support)

my config:

config :samly, Samly.Provider,
  idp_id_from: :path_segment,
  service_providers: [
    %{
      id: "entsp",
      entity_id: "http://enterprise.local:4000",
      certfile: "priv/keys/samly.crt",
      keyfile: "priv/keys/samly.pem"
    }
  ],
  identity_providers: [
    %{
      id: "entidp",
      sp_id: "entsp",
      metadata_file: "priv/idp/metadata.xml",
      nameid_format: "urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress",
      pre_session_create_pipeline: Enterprise.Modules.Plugs.Samly,
      use_redirect_for_req: true,
    }
  ]

When i initiate signin request i get an error Invalid ACL url 'nil'

The decoded SAML request data is

<samlp:AuthnRequest xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" IssueInstant="2018-07-15T19:06:13Z" Version="2.0" Destination="http://domain.com/login" AssertionConsumerServiceURL="nil" ProtocolBinding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST" ID="id15316815732765741722466">
<saml:Issuer>http://enterprise.local:4000</saml:Issuer>
<samlp:NameIDPolicy Format="urn:oasis:names:tc:SAML:2.0:nameid-format:transient"/>
</samlp:AuthnRequest>

Please how is AssertionConsumerServiceURL suppose to be set?