init() function execution order in Go packages

Multiple init() functions across files and packages execute in a specific but non-obvious order, causing surprises when global state depends on another init() having run first.

Understand the guaranteed order and design accordingly:

Order:
1. All imported packages are initialised first (recursively)
2. Within a package, files are processed in alphabetical order
3. Within a file, package-level vars are initialised top-to-bottom
4. init() functions run after all vars are set, in file order
5. Multiple init() in the same file run top-to-bottom

// a.go
func init() { fmt.Println("a.go init") }

// b.go
func init() { fmt.Println("b.go init") }
// Output: a.go init, then b.go init

Avoid cross-init() dependencies. Use explicit initialization functions called from main() when order matters.

The Go spec guarantees that imported packages initialise before the importing package. Within a package, the order is deterministic (alphabetical by filename) but relying on it is fragile if files are renamed.