I am using Vapor to write a simple web app. I have an entity to save session info into a database. The code for this entity is as follows:

struct SessionToken: Model{
    var exists: Bool = false
    var id: Node?
    var username: String
    var accessToken: String
    var expiryDate: String

    init(username: String, accessToken: String, expiryDate: String) {
        self.username = username
        self.accessToken = accessToken
        self.expiryDate = expiryDate
    }

    init(node: Node, in context: Context) throws {
        try self.id = node.extract("id")
        try self.username = node.extract("username")
        try self.accessToken = node.extract("accessToken")
        try self.expiryDate = node.extract("expiryDate")
    }


    func makeNode(context: Context) throws -> Node {
        let sessionToken = try Node(node:["id": id, "username": username, "accessToken": accessToken, "expiryDate": expiryDate])
        return sessionToken
    }


    static func prepare(_ database: Database) throws {
        try database.create("sessiontokens"){ sessiontokens in
            sessiontokens.id()
            sessiontokens.string("username")
            sessiontokens.string("accessToken")
            sessiontokens.string("expiryDate")

        }
    }

    static func revert(_ database: Database) throws {
        try database.delete("sessiontokens")
    }

}

I enter some fake info into the database, but when I query the database with the following code:

let token = try SessionToken.query().filter("username", "user@email.com").first()

I get an error: Could not initialize SessionToken, skipping: unableToConvert(node: nil, expected: "String")

The funny thing is that when I replace SessionToken with any other entity in the project the code works just fine. The only entity I am having trouble fetching any info from the database is SessionToken and it has been frustrating me since last night!

I would really appreciate it if someone could point me in the right direction to solve this problem.

P.S. I am using Postgres.