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: finalizer.go
    path of file: ./repos/wormhole/node/pkg/watchers/near
    
    the code of the file until where you have to start completion: package near

import (
	"context"
	"errors"

	"github.com/certusone/wormhole/node/pkg/watchers/near/nearapi"
	lru "github.com/hashicorp/golang-lru"
	"go.uber.org/zap"
)

type Finalizer struct {
	// internal cache of which blocks have been finalized, mapping blockHack => blockTimestamp.
	// The timestamp is per
    
func (f Finalizer) setFinalizedHash(logger *zap.Logger, ctx context.Context, blockHash string) error { //nolint Ignore unused function for now; might come in handy later
	logger.Debug("setFinalizedHash()", zap.String("blockHash", blockHash))
	// SECURITY defense-in-depth: don't cache obviously corrupted data.
	if nearapi.IsWellFormedHash(blockHash) != nil {
		return errors.New("blockHash length is not the expected length")
	}

	block, err := f.nearAPI.GetBlock(ctx, blockHash)
	if err != nil {
		return err
	}

	f.finalizedBlocksCache.Add(blockHash, block.Header)
	return nil
}