FormFile
MultipartForm files can be retrieved by name, the first file from the given key is returned.
func (c *Ctx) FormFile(key string) (*multipart.FileHeader, error)
app.Post("/", func(c *fiber.Ctx) error {
// Get first file from form field "document":
file, err := c.FormFile("document")
// Save file to root directory:
return c.SaveFile(file, fmt.Sprintf("./%s", file.Filename))
})