x/benchmarks: fix go vet warnings

Here are go vet warnings for this repository:

lang.org/x/benchmarks/driver
driver/driver.go:375:2: unreachable code
driver/driver.go:376:2: unreachable code
third_party/biogo-examples/igor/igor/cluster.go:51:9: github.com/biogo/store/interval.IntRange struct literal uses unkeyed fields
sweet/benchmarks/biogo-igor/igor.go:68:30: golang.org/x/benchmarks/third_party/biogo-examples/igor/igor.GroupConfig struct literal uses unkeyed fields

This patch will fix the above warnings.

Change-Id: Id36cc3fa951072d374b843eff9abd769874d3835
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/642895
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
diff --git a/driver/driver.go b/driver/driver.go
index ba32d3f..37f9af7 100644
--- a/driver/driver.go
+++ b/driver/driver.go
@@ -372,8 +372,6 @@
 	default:
 		return 10 * base
 	}
-	panic("unreachable")
-	return 0
 }
 
 func min(a, b uint64) uint64 {
diff --git a/sweet/benchmarks/biogo-igor/igor.go b/sweet/benchmarks/biogo-igor/igor.go
index 8f1a270..b44cf9d 100644
--- a/sweet/benchmarks/biogo-igor/igor.go
+++ b/sweet/benchmarks/biogo-igor/igor.go
@@ -66,9 +66,9 @@
 			Procs:             runtime.GOMAXPROCS(0),
 		})
 		cc := igor.Group(clusters, igor.GroupConfig{
-			pileDiff,
-			imageDiff,
-			false,
+			PileDiff:  pileDiff,
+			ImageDiff: imageDiff,
+			Classic:   false,
 		})
 		err = igor.WriteJSON(cc, &out)
 		if err != nil {
diff --git a/third_party/biogo-examples/igor/igor/cluster.go b/third_party/biogo-examples/igor/igor/cluster.go
index 26f202d..0c19bf4 100644
--- a/third_party/biogo-examples/igor/igor/cluster.go
+++ b/third_party/biogo-examples/igor/igor/cluster.go
@@ -48,7 +48,7 @@
 	return pi.p.Start() < b.End && pi.p.End() > b.Start
 }
 func (pi pileInterval) Range() interval.IntRange {
-	return interval.IntRange{pi.p.Start(), pi.p.End()}
+	return interval.IntRange{Start: pi.p.Start(), End: pi.p.End()}
 }
 
 // ClusterConfig specifies Cluster behaviour.