What function in fiber makes logic similar to func (c *Context) Set(key string, value any) in gin?

What function in fiber makes logic similar to func (c *Context) Set(key string, value any) in gin?

I was looking for a function to write a key / value pair in a certain context, but I did not find it, please tell me if there is such an opportunity

Looks like (*Ctx).Locals is what you want.

The following content is copied from the official doc:

Locals

A method that stores variables scoped to the request and, therefore, are available only to the routes that match the request.

Signature

func (c *Ctx) Locals(key interface{}, value ...interface{}) interface{}

Example

app.Use(func(c *fiber.Ctx) error {
  c.Locals("user", "admin")
  return c.Next()
})

app.Get("/admin", func(c *fiber.Ctx) error {
  if c.Locals("user") == "admin" {
    return c.Status(fiber.StatusOK).SendString("Welcome, admin!")
  }
  return c.SendStatus(fiber.StatusForbidden)
})