Reading Struct Tags

Struct tags are the thin string of metadata that turns plain Go structs into JSON payloads, SQL rows, validated input, and configuration objects. The previous chapter covered how to walk a struct's fields with reflection; this one zooms in on the reflect.StructTag value attached to each field, the conventions every popular library has agreed on, and how to parse tags yourself when you need to build something custom. This lesson builds a small but real validator that reads validate:"..." tags and rejects bad input.