How to declare a variable in a graphql query struct for pagination with Hasura Go client?

Question

Having an issue when executing a paginated query with Hasura graphql Go client github.com/hasura/go-graphql-client but haven't found the answer in the docs. The graphql query is as follows (simplified it for this question):

query ($after: String) {
    entity (first: 10, after: $after) {
        pageInfo {
          hasNextPage
          endCursor
        }
        nodes {
          name
        }
    }
}

The Go code

type Query struct {
    Entity struct {
        PageInfo struct {
            HasNextPage bool   `graphql:"hasNextPage"`
            EndCursor   string `graphql:"endCursor"`
        } `graphql:"pageInfo"`

        Nodes []struct {
            Name string `graphql:"name"`
        } `graphql:"nodes`
    } `graphql:"entity(first: 10, after: $after)"`
}

var q Query

var after string = ""
var hasNextPage bool = true

variables := map[string]interface{}{
    "after": after,
}

err := client.Query(context.Background(), &q, variables)

The thing is that I don't know how to declare the $after variable and when executed it throws an error

"Failed to parse \"String\": EOF while parsing a value at line 1 column 0"

Anyone can help with the issue? Thanks in advance.

Answer 1

The code is ok, the problem is that the query throws an error if the after variable (cursor Id) is empty or has a value that doesn't match with a cursor.

So the solution was to do a first query without the $after variable like this

type Query struct {
    Entity struct {
        PageInfo struct {
            HasNextPage bool   `graphql:"hasNextPage"`
            EndCursor   string `graphql:"endCursor"`
        } `graphql:"pageInfo"`

        Nodes []struct {
            Name string `graphql:"name"`
        } `graphql:"nodes`
    } `graphql:"entity(first: 10)"`
}

...

variables := map[string]interface{}{}

and once we have a right value for Endcursor we can do the subsequent queries with that value for the $after variable like in the question

type Query struct {
    Entity struct {
        PageInfo struct {
            HasNextPage bool   `graphql:"hasNextPage"`
            EndCursor   string `graphql:"endCursor"`
        } `graphql:"pageInfo"`

        Nodes []struct {
            Name string `graphql:"name"`
        } `graphql:"nodes`
    } `graphql:"entity(first: 10, after: $after)"`
}

...

variables := map[string]interface{}{
    "after": after,
}

Maybe there's a better way to do it without duplicating code, but haven't found it.