<h3 id="Package_initialization">Package initialization</h3>

<p>
Within a package, package-level variable initialization proceeds stepwise,
with each step selecting the variable earliest in <i>declaration order</i>
which has no dependencies on uninitialized variables.
</p>

<p>
More precisely, a package-level variable is considered <i>ready for
initialization</i> if it is not yet initialized and either has

pkg go/version, func Lang(string) string #62039
pkg html/template, const ErrJSTemplate //deprecated #61619
pkg io, method (*SectionReader) Outer() (ReaderAt, int64, int64) #61870
pkg log/slog, func SetLogLoggerLevel(Level) Level #62418
pkg math/big, method (*Rat) FloatPrec() (int, bool) #50489
pkg math/rand/v2, func ExpFloat64() float64 #61716
pkg math/rand/v2, func Float32() float32 #61716
pkg math/rand/v2, func Float64() float64 #61716

}

// RegisterCompressor registers or overrides a custom compressor for a specific
// method ID. If a compressor for a given method is not found, [Writer] will
// default to looking up the compressor at the package level.
func (w *Writer) RegisterCompressor(method uint16, comp Compressor) {
	if w.compressors == nil {
		w.compressors = make(map[uint16]Compressor)
	}
	w.compressors[method] = comp
}