diff --git a/db_test.go b/db_test.go
index 93d46f2b8..89d329b92 100644
--- a/db_test.go
+++ b/db_test.go
@@ -89,7 +89,7 @@ func TestDataAvailableOnlyAfterCommit(t *testing.T) {
 
 	seriesSet = query(t, querier, labels.NewEqualMatcher("foo", "bar"))
 
-	testutil.Equals(t, seriesSet, map[string][]sample{`{foo="bar"}`: []sample{{t: 0, v: 0}}})
+	testutil.Equals(t, seriesSet, map[string][]sample{`{foo="bar"}`: {{t: 0, v: 0}}})
 }
 
 func TestDataNotAvailableAfterRollback(t *testing.T) {
@@ -156,7 +156,7 @@ func TestDBAppenderAddRef(t *testing.T) {
 	res := query(t, q, labels.NewEqualMatcher("a", "b"))
 
 	testutil.Equals(t, map[string][]sample{
-		labels.FromStrings("a", "b").String(): []sample{
+		labels.FromStrings("a", "b").String(): {
 			{t: 123, v: 0},
 			{t: 124, v: 1},
 			{t: 125, v: 0},
@@ -310,7 +310,7 @@ func TestSkippingInvalidValuesInSameTxn(t *testing.T) {
 	ssMap := query(t, q, labels.NewEqualMatcher("a", "b"))
 
 	testutil.Equals(t, map[string][]sample{
-		labels.New(labels.Label{"a", "b"}).String(): []sample{{0, 1}},
+		labels.New(labels.Label{"a", "b"}).String(): {{0, 1}},
 	}, ssMap)
 
 	testutil.Ok(t, q.Close())
@@ -329,7 +329,7 @@ func TestSkippingInvalidValuesInSameTxn(t *testing.T) {
 	ssMap = query(t, q, labels.NewEqualMatcher("a", "b"))
 
 	testutil.Equals(t, map[string][]sample{
-		labels.New(labels.Label{"a", "b"}).String(): []sample{{0, 1}, {10, 3}},
+		labels.New(labels.Label{"a", "b"}).String(): {{0, 1}, {10, 3}},
 	}, ssMap)
 	testutil.Ok(t, q.Close())
 }
diff --git a/fileutil/sync_linux.go b/fileutil/sync_linux.go
index 1145904bf..1bbced915 100644
--- a/fileutil/sync_linux.go
+++ b/fileutil/sync_linux.go
@@ -31,4 +31,4 @@ func Fsync(f *os.File) error {
 // to be correctly handled.
 func Fdatasync(f *os.File) error {
 	return syscall.Fdatasync(int(f.Fd()))
-}
\ No newline at end of file
+}
diff --git a/head_test.go b/head_test.go
index 4ebf89164..caf4d652c 100644
--- a/head_test.go
+++ b/head_test.go
@@ -179,17 +179,17 @@ func TestHead_Truncate(t *testing.T) {
 	testutil.Assert(t, postingsC1 == nil, "")
 
 	testutil.Equals(t, map[string]struct{}{
-		"":  struct{}{}, // from 'all' postings list
-		"a": struct{}{},
-		"b": struct{}{},
-		"1": struct{}{},
-		"2": struct{}{},
+		"":  {}, // from 'all' postings list
+		"a": {},
+		"b": {},
+		"1": {},
+		"2": {},
 	}, h.symbols)
 
 	testutil.Equals(t, map[string]stringset{
-		"a": stringset{"1": struct{}{}, "2": struct{}{}},
-		"b": stringset{"1": struct{}{}},
-		"":  stringset{"": struct{}{}},
+		"a": {"1": struct{}{}, "2": struct{}{}},
+		"b": {"1": struct{}{}},
+		"":  {"": struct{}{}},
 	}, h.values)
 }
 
diff --git a/index/index_test.go b/index/index_test.go
index 83b6ef657..f1b4d4181 100644
--- a/index/index_test.go
+++ b/index/index_test.go
@@ -192,12 +192,12 @@ func TestIndexRW_Postings(t *testing.T) {
 	}
 
 	err = iw.AddSymbols(map[string]struct{}{
-		"a": struct{}{},
-		"b": struct{}{},
-		"1": struct{}{},
-		"2": struct{}{},
-		"3": struct{}{},
-		"4": struct{}{},
+		"a": {},
+		"b": {},
+		"1": {},
+		"2": {},
+		"3": {},
+		"4": {},
 	})
 	testutil.Ok(t, err)
 
diff --git a/index/postings_test.go b/index/postings_test.go
index 9f8f71220..e7e2e61ca 100644
--- a/index/postings_test.go
+++ b/index/postings_test.go
@@ -371,7 +371,7 @@ func TestRemovedNextStackoverflow(t *testing.T) {
 	for rp.Next() {
 		gotElem = true
 	}
-	
+
 	testutil.Ok(t, rp.Err())
 	testutil.Assert(t, !gotElem, "")
 }
diff --git a/wal.go b/wal.go
index 8a2095aed..c1b9f6b06 100644
--- a/wal.go
+++ b/wal.go
@@ -937,7 +937,7 @@ func (r *walReader) Read(
 				series = v.([]RefSeries)
 			}
 
-			err := r.decodeSeries(flag, b, &series)
+			err = r.decodeSeries(flag, b, &series)
 			if err != nil {
 				err = errors.Wrap(err, "decode series entry")
 				break
@@ -958,7 +958,7 @@ func (r *walReader) Read(
 				samples = v.([]RefSample)
 			}
 
-			err := r.decodeSamples(flag, b, &samples)
+			err = r.decodeSamples(flag, b, &samples)
 			if err != nil {
 				err = errors.Wrap(err, "decode samples entry")
 				break
@@ -980,7 +980,7 @@ func (r *walReader) Read(
 				deletes = v.([]Stone)
 			}
 
-			err := r.decodeDeletes(flag, b, &deletes)
+			err = r.decodeDeletes(flag, b, &deletes)
 			if err != nil {
 				err = errors.Wrap(err, "decode delete entry")
 				break