Add progress reporting to json_importer (#2494)

Fixes #2494

go/util/progressreader/reader.go

@@ -29,7 +29,7 @@ func (r *reader) Read(p []byte) (n int, err error) {
 	n, err = r.inner.Read(p)
 	r.seen += uint64(n)
 
-	if now := time.Now(); now.Sub(r.lastTime) >= status.Rate {
+	if now := time.Now(); now.Sub(r.lastTime) >= status.Rate || err == io.EOF {
 		r.cb(r.seen)
 		r.lastTime = now
 	}

samples/go/json-import/json_importer.go

@@ -11,10 +11,14 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"time"
 
 	"github.com/attic-labs/noms/go/d"
 	"github.com/attic-labs/noms/go/spec"
 	"github.com/attic-labs/noms/go/util/jsontonoms"
+	"github.com/attic-labs/noms/go/util/progressreader"
+	"github.com/attic-labs/noms/go/util/status"
+	"github.com/dustin/go-humanize"
 	flag "github.com/juju/gnuflag"
 )
 
@@ -48,10 +52,17 @@ func main() {
 	defer res.Body.Close()
 
 	var jsonObject interface{}
-	err = json.NewDecoder(res.Body).Decode(&jsonObject)
+	start := time.Now()
+	r := progressreader.New(res.Body, func(seen uint64) {
+		elapsed := time.Since(start).Seconds()
+		rate := uint64(float64(seen) / elapsed)
+		status.Printf("%s decoded in %ds (%s/s)...", humanize.Bytes(seen), int(elapsed), humanize.Bytes(rate))
+	})
+	err = json.NewDecoder(r).Decode(&jsonObject)
 	if err != nil {
 		log.Fatalln("Error decoding JSON: ", err)
 	}
+	status.Done()
 
 	_, err = ds.CommitValue(jsontonoms.NomsValueFromDecodedJSON(jsonObject, true))
 	d.PanicIfError(err)