How can internal details of an object be hidden in the Go language?

In Go, the internal details of an object (structure) can be hidden by exporting fields and methods. If the name of a field or method starts with an uppercase letter, it is exported and accessible from other packages. If it starts with a lowercase letter, the field or method is private to the package and not accessible from outside.

Example:

package mypackage

type User struct {
    Name string // exported field
    age  int    // private field
}

func (u *User) GetAge() int { // exported method to access the private field
    return u.age
}

Thus, internal details can be hidden by making fields and methods unexported (with lowercase letters) and providing access through exported methods.