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: dns_resolver.go
    path of file: ./repos/devspace/vendor/google.golang.org/grpc/internal/resolver/dns
    
    the code of the file until where you have to start completion: /*
 *
 * Copyright 2018 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions 
    
func (d *dnsResolver) watcher() {
	defer d.wg.Done()
	backoffIndex := 1
	for {
		state, err := d.lookup()
		if err != nil {
			// Report error to the underlying grpc.ClientConn.
			d.cc.ReportError(err)
		} else {
			err = d.cc.UpdateState(*state)
		}

		var timer *time.Timer
		if err == nil {
			// Success resolving, wait for the next ResolveNow. However, also wait 30 seconds at the very least
			// to prevent constantly re-resolving.
			backoffIndex = 1
			timer = newTimerDNSResRate(minDNSResRate)
			select {
			case <-d.ctx.Done():
				timer.Stop()
				return
			case <-d.rn:
			}
		} else {
			// Poll on an error found in DNS Resolver or an error received from ClientConn.
			timer = newTimer(backoff.DefaultExponential.Backoff(backoffIndex))
			backoffIndex++
		}
		select {
		case <-d.ctx.Done():
			timer.Stop()
			return
		case <-timer.C:
		}
	}
}