title: Graphql query erroring with 'Unknown type Int' with Apollo Client and graphql-go
body: <p>I've got a graphql server implemented with <a href="https://github.com/graphql-go" rel="noreferrer">graphql-go</a>, and I'm using Apollo on the front end. Simple queries without arguments, and mutations using input object types work fine, but for some reason passing a scalar type argument in a query returns the error:</p>
  
  <pre><code>[{"message":"Unknown type \"Int\".","locations":[{"line":1,"column":19}]}]
  </code></pre>
  
  <p>My use could not be simpler; on the client side, my query is:</p>
  
  <pre><code>export const GET_CLIENT = gql`
    query client($id: Int) {
    client(id: $id) {
      id
      name
    }
  }`
  </code></pre>
  
  <p>which is used in a component like so:</p>
  
  <pre><code>&lt;Query
    query={GET_CLIENT}
    variables={{
      id: 1
    }} /&gt;
  </code></pre>
  
  <p>which resolves to this field on the backend:</p>
  
  <pre><code>// ClientQuery takes an ID and returns one client or nil
  var ClientQuery = &amp;graphql.Field{
  Type: ClientType,
  Args: graphql.FieldConfigArgument{
      "id": &amp;graphql.ArgumentConfig{
          Type: graphql.Int,
      },
  },
  Resolve: func(p graphql.ResolveParams) (interface{}, error) {
      return p.Context.Value("service").(*model.Service).FindClientByID(id)
  },
  }
  </code></pre>
  
  <p>I've tried passing input objects, strings, etc. but it seems that no query arguments, scalar or otherwise are ever satisfied on the backend. I've tried both master and v0.7.5 of graphql-go. Am I missing something? Help very much appreciated, it feels weird for something this basic to be such a huge blocker.</p>