Lectures

We break down structs in Go: how to declare a new type via type … struct, what fields are and how to access them via the selector ., how zero value works (including nil for map/ slice and pointers), how exported and unexported fields differ ( Title vs title), and why you sometimes pass * Task instead of Task.

We break down composite struct literals in Go: how to create values via T{...}, how positional initialization differs from named initialization ( Field : "value"), why positional style is risky during refactoring, how partial initialization and the zero value work, why you cannot mix styles, how to get a pointer via & T{...}, and how to conveniently build slices of structs and multi-line literals (with the required trailing comma).

We break down what “comparable” ( comparable) means in Go: why you can compare a struct via == only when all its fields are comparable, what breaks comparability (for example, slice, map, func), why interface fields are tricky (a panic at runtime is possible), how pointer comparisons ( * T) can be interpreted differently, and why comparability is directly tied to whether a value can be used as a key in a map.

We break down what struct tags are in Go and why they are just string labels for libraries. We learn how to “read” tags like json : "title,omitempty": where the field name is separated from options by a comma, what omitempty means, how the special case json : "-" works, how to combine multiple conventions in a single tag ( json + db), and which mistakes most often occur when working with tags.

We break down why “just a struct” still doesn’t mean a correct model: we introduce the concept of invariants and learn to protect data at the boundary (stdin → parse → normalize → validate). Using a mini‑model Task as an example, we build rules ( ID > 0, non-empty Title after TrimSpace, valid Status), implement the ValidateTask and NewTask patterns, and discuss common mistakes when working with the zero value and validation.