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: routing.go
    path of file: ./repos/sealer/vendor/github.com/ipfs/go-namesys
    
    the code of the file until where you have to start completion: package namesys

import (
	"context"
	"strings"
	"time"

	proto "github.com/gogo/protobuf/proto"
	cid "github.com/ipfs/go-cid"
	ipns "github.com/ipfs/go-ipns"
	pb "github.com/ipfs/go-ipns/pb"
	logging "github.com/ipfs/go-log"
	path "github.com/ipfs/go-path"
	opts "github.com/ipfs/interface-go-ipfs-core/options/namesys"
	peer "github.com/libp2p/go-libp2p-core/peer"
	routing "github.com/libp2p/go-libp2p-core/routing"
	dht "github.com/libp2p/go-libp2p-kad-dht"
	mh "github.com/multiformats/go-multihash"
)

var log = logging.Logger("namesys")

// IpnsResolver implements NSResolver for the main IPFS SFS-like naming
type IpnsResolver struct {
	routing routing.ValueStore
}

// NewIpnsResolver constructs a name resolver using the IPFS Routing system
// to implement SFS-like naming on top.
func NewIpnsResolver(route routing.ValueStore) *IpnsResolver {
	if route == nil {
		panic("attempt to create resolver with nil routing system")
	}
	return &IpnsResolver{
		routing: route,
	}
}

// Resolve implements Resolver.
func (r *IpnsResolver) Resolve(ctx context.Context, name string, options ...opts.ResolveOpt) (path.Path, error) {
	return resolve(ctx, r, name, opts.ProcessOpts(options))
}

// ResolveAsync implements Resolver.
func (r *IpnsResolver) ResolveAsync(ctx context.Context, name string, options ...opts.ResolveOpt) <-chan Result {
	return resolveAsync(ctx, r, name, opts.ProcessOpts(options))
}

// resolveOnce implements resolver. Uses the IPFS routing system to
// resolve SFS-like names.
func (r *IpnsResolver) resolveOnceAsync(ctx context.Context, name string, options opts.ResolveOpts) <-chan onceResult {
	out := make(chan onceResult, 1)
	log.Debugf("RoutingResolver resolving %s", name)
	cancel := func() {}

	if options.DhtTimeout != 0 {
		// Resolution must complete within the timeout
		ctx, cancel = context.WithTimeout(ctx, options.DhtTimeout)
	}

	name = strings.TrimPrefix(name, "/ipns/")

	pid, err := peer.Decode(name)
	if err != nil {
		log.Debugf("RoutingResolver: could not convert public key hash %s to peer ID: %s\n", name, err)
		out <- onceResult{err: err}
		close(out)
		cancel()
		return out
	}

	// Use the routing system to get the name.
	// Note that the DHT will call the ipns validator when retrieving
	// the value, which in turn verifies the ipns record signature
	ipnsKey := ipns.RecordKey(pid)

	vals, err := r.routing.SearchValue(ctx, ipnsKey, dht.Quorum(int(options.DhtRecordCount)))
	if err != nil {
		log.Debugf("Routi
    
func (r *IpnsResolver) resolveOnceAsync(ctx context.Context, name string, options opts.ResolveOpts) <-chan onceResult {
	out := make(chan onceResult, 1)
	log.Debugf("RoutingResolver resolving %s", name)
	cancel := func() {}

	if options.DhtTimeout != 0 {
		// Resolution must complete within the timeout
		ctx, cancel = context.WithTimeout(ctx, options.DhtTimeout)
	}

	name = strings.TrimPrefix(name, "/ipns/")

	pid, err := peer.Decode(name)
	if err != nil {
		log.Debugf("RoutingResolver: could not convert public key hash %s to peer ID: %s\n", name, err)
		out <- onceResult{err: err}
		close(out)
		cancel()
		return out
	}

	// Use the routing system to get the name.
	// Note that the DHT will call the ipns validator when retrieving
	// the value, which in turn verifies the ipns record signature
	ipnsKey := ipns.RecordKey(pid)

	vals, err := r.routing.SearchValue(ctx, ipnsKey, dht.Quorum(int(options.DhtRecordCount)))
	if err != nil {
		log.Debugf("RoutingResolver: dht get for name %s failed: %s", name, err)
		out <- onceResult{err: err}
		close(out)
		cancel()
		return out
	}

	go func() {
		defer cancel()
		defer close(out)
		for {
			select {
			case val, ok := <-vals:
				if !ok {
					return
				}

				entry := new(pb.IpnsEntry)
				err = proto.Unmarshal(val, entry)
				if err != nil {
					log.Debugf("RoutingResolver: could not unmarshal value for name %s: %s", name, err)
					emitOnceResult(ctx, out, onceResult{err: err})
					return
				}

				var p path.Path
				// check for old style record:
				if valh, err := mh.Cast(entry.GetValue()); err == nil {
					// Its an old style multihash record
					log.Debugf("encountered CIDv0 ipns entry: %s", valh)
					p = path.FromCid(cid.NewCidV0(valh))
				} else {
					// Not a multihash, probably a new style record
					p, err = path.ParsePath(string(entry.GetValue()))
					if err != nil {
						emitOnceResult(ctx, out, onceResult{err: err})
						return
					}
				}

				ttl := DefaultResolverCacheTTL
				if entry.Ttl != nil {
					ttl = time.Duration(*entry.Ttl)
				}
				switch eol, err := ipns.GetEOL(entry); err {
				case ipns.ErrUnrecognizedValidity:
					// No EOL.
				case nil:
					ttEol := time.Until(eol)
					if ttEol < 0 {
						// It *was* valid when we first resolved it.
						ttl = 0
					} else if ttEol < ttl {
						ttl = ttEol
					}
				default:
					log.Errorf("encountered error when parsing EOL: %s", err)
					emitOnceResult(ctx, out, onceResult{err: err})
					return
				}

				emitOnceResult(ctx, out, onceResult{value: p, ttl: ttl})
			case <-ctx.Done():
				return
			}
		}
	}()

	return out
}