You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: metadata.go
    path of file: ./repos/gotosocial/vendor/github.com/cilium/ebpf/asm
    
    the code of the file until where you have to start completion: package asm

// Metadata contains metadata about an instruction.
type Metadata struct {
	head *metaElement
    
func (m *Metadata) Set(key, value interface{}) {
	if e := m.find(key); e != nil {
		if e.value == value {
			// Key is present and the value is the same. Nothing to do.
			return
		}

		// Key is present with a different value. Create a copy of the list
		// which doesn't have the element in it.
		m.remove(e)
	}

	// m.head is now a linked list that doesn't contain key.
	if value == nil {
		return
	}

	m.head = &metaElement{key: key, value: value, next: m.head}
}