Handling foreign key on a post route Prisma / MYSQL

Question

i would like to understand why my post route doesn't work, the error comes out like :

ReferenceError: author_id is not defined

Here is my code following :

Schema Prisma :

model users {
  user_id   Int      @id @default(autoincrement()) @db.UnsignedInt
  firstName String   @db.VarChar(255)
  lastName  String   @db.VarChar(255)
  email     String   @unique(map: "email") @db.VarChar(255)
  password  String   @db.VarChar(255)  
  createdAt DateTime @default(now())
  isAdmin   Boolean  @default(false)
  post post[]
  comments comments[]
}

model post {
  post_id  Int    @id @default(autoincrement()) @db.UnsignedInt
  title    String @db.VarChar(50)
  content  String @db.Text
  author_id Int @db.UnsignedInt
  users     users @relation(fields: [author_id], references: [user_id])
  comments   comments[]

  @@index([author_id], name: "FK1_AUTHORID")
}

And my post.route.js :

router.post('/', async (req, res) => {
    try {
        const { title, content } = req.body;
        const result = await prisma.post.create({
            data: {
                title,
                content,
                users: {
                    connect: {
                            user_id: author_id
                    }
                },
            },
        })
        res.json(result)
    }
    catch(e) {
        console.log(e);
    }
});

Everything on the database is up to date, the tables are exactly like the schema i sent