Section 9 of 11

Packages, imports & layout

A package is a directory. Capitalization is the access modifier.

a real module

myapp/
  go.mod                     module github.com/me/myapp
  cmd/server/main.go         -> go build ./cmd/server   -> ./server
  cmd/migrate/main.go        -> go build ./cmd/migrate  -> ./migrate
  internal/store/store.go    COMPILER-ENFORCED private to this module
  pkg/                       optional, public, often skipped

A package == a directory. Every .go file in it declares the same package name. No splitting a package across dirs.
Any package named main with a func main() compiles to one binary — one module can produce several.
internal/ is a hardcoded rule in the toolchain, not a convention: only code rooted at its parent may import it.
NO circular imports. The compiler rejects them outright, which forces your dependency graph to be a DAG.
Unused imports are compile errors. goimports (on save) manages them for you.
import _ "net/http/pprof" is a blank import: run its init() for the side effect only.
Inside a package everything sees everything; capitalization only gates access ACROSS packages.
http.ListenAndServe is a package qualifier + function — Go has no statics because package-level funcs already are that.

Capitalization, structs, and the stdlib as namespace

go.dev playground

Try it: Rename Name to name and the json output loses the field — encoding/json can only see exported fields.