Can you name the main types of keys used in relational databases?

Main types of keys in relational databases:

• Primary Key — a unique identifier for a record in a table. Cannot contain NULL and must be unique.
• Foreign Key — a field or set of fields that references the primary key of another table, establishing a relationship between tables.
• Unique Key — guarantees the uniqueness of values in a column or set of columns, allows NULLs (in some DBMS).
• Surrogate Key — an artificial key, usually an auto-incremented number, without business meaning.
• Composite Key — a key consisting of multiple columns that together ensure uniqueness.

An example in Go using a structure to describe keys is not necessary, as this is a database concept, but when working with ORM, it is important to specify keys correctly.