Suppose a function <code>G</code> defers a function <code>D</code> that calls
<code>recover</code> and a panic occurs in a function on the same goroutine in which <code>G</code>
is executing.
When the running of deferred functions reaches <code>D</code>,
the return value of <code>D</code>'s call to <code>recover</code> will be the value passed to the call of <code>panic</code>.
If <code>D</code> returns normally, without starting a new

	"strings"
	"sync"
)

var (
	root    = flag.String("root", "http://localhost:6060", "Root to crawl")
	verbose = flag.Bool("verbose", false, "verbose")
)

var wg sync.WaitGroup        // outstanding fetches
var urlq = make(chan string) // URLs to crawl

// urlFrag is a URL and its optional #fragment (without the #)
type urlFrag struct {
	url, frag string
}

var (
	mu          sync.Mutex

Suppose a function <code>G</code> defers a function <code>D</code> that calls
<code>recover</code> and a panic occurs in a function on the same goroutine in which <code>G</code>
is executing.
When the running of deferred functions reaches <code>D</code>,
the return value of <code>D</code>'s call to <code>recover</code> will be the value passed to the call of <code>panic</code>.
If <code>D</code> returns normally, without starting a new

		spd = append(spd, sparseEntry{Offset: offset, Length: length})
		sparseMap = sparseMap[2:]
	}
	return spd, nil
}

// Read reads from the current file in the tar archive.
// It returns (0, io.EOF) when it reaches the end of that file,
// until [Next] is called to advance to the next file.
//
// If the current file is sparse, then the regions marked as a hole
// are read back as NUL-bytes.
//