Unsupported relations in gorm

I'm trying to Preload data from a One to Many relationship, yet I always get an "ApiKeys: unsupported relations for schema Client" error. (The reason structs are pointers is because I'm using gqlgen and that's the default configuration)

type Client struct {
    //  Client ID
    ID int `json:"id"`
    UserName string `json:"userName"`
    //  Client login hashed password
    Password string `json:"password"`
    //  ApiKeys
    APIKeys []*APIKey `json:"apiKeys"`
}
    
type APIKey struct {
    //  ApiKey Index
    ID int `json:"id"`
    //  ApiKey Value
    Key string `json:"key"`
    //  ApiKey Client Relation
    ClientID int `json:"clientID"`
    //  ApiKey Client Info
    Client *Client `json:"client"`
}

And this is the function that calls the Preload of ApiKeys.

func (r *queryResolver) ClientInfoResolver(username string, password string) (*model.Client, error) {
    var clients []*model.Client
    var client *model.Client
    query := r.Resolver.DB
    
    query = query.Where("user_name = ? AND password = ?", username, password).Preload("ApiKeys").Find(&clients)
    
    if query.Error != nil {
        return client, query.Error
    }
    return clients[0], nil
}

I understand by gorm's documentation that the foreign key for the relation is ClientID, despite not being explicit (doesn't work by specifying it either) am I understanding something wrong here?

You list APIKeys as the struct field name but try and use ApiKeys as the FK.

.Preload("ApiKeys")
// Should be
.Preload("APIKeys")

Or, if you want to use ApiKeys as the foreign key, use a Gorm struct tag to do this.

Full working example

package main

import (
    "fmt"
    "gorm.io/driver/sqlite"
    "gorm.io/gorm"
)

type Client struct {
    //  ApiKey Index
    ID int `json:"id"`
    UserName string `json:"userName"`
    //  Client login hashed password
    Password string `json:"password"`
    //  ApiKeys
    APIKeys []*APIKey `json:"apiKeys"`
}

type APIKey struct {
    //  ApiKey Index
    ID int `json:"id"`
    //  ApiKey Value
    Key string `json:"key"`
    //  ApiKey Client Relation
    ClientID int `json:"clientID"`
    //  ApiKey Client Info
    Client *Client `json:"client"`
}

func main() {

    db, err := gorm.Open(sqlite.Open("many2many.db"), &gorm.Config{})
    if err != nil {
        panic("failed to connect database")
    }

    // Migrate the schema
    err = db.AutoMigrate(&APIKey{}, &Client{})
    if err != nil {
        fmt.Print(err)
    }

    clientOne := Client{
        UserName:          "Client One",
    }
    db.Create(&clientOne)

    apiKeyOne := APIKey{
        Key:"one",
        Client: &clientOne,
    }
    apiKeyTwo := APIKey{
        Key:"two",
        Client: &clientOne,
    }

    db.Create(&apiKeyOne)
    db.Create(&apiKeyTwo)

    // Fetch from DB
    fetchedClient := Client{}

    db.Debug().Preload("APIKeys").Find(&fetchedClient, clientOne.ID)
    fmt.Println(fetchedClient)

    db.Delete(&clientOne)
    db.Delete(&apiKeyOne)
    db.Delete(&apiKeyTwo)
}