fix go 1.15 errors (#5277)

## Description

fix golang 1.15 errors. 

Closes: #XXX

libs/cmap/cmap_test.go

@@ -60,10 +60,10 @@ func TestContains(t *testing.T) {
 func BenchmarkCMapHas(b *testing.B) {
 	m := NewCMap()
 	for i := 0; i < 1000; i++ {
-		m.Set(string(i), i)
+		m.Set(string(rune(i)), i)
 	}
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		m.Has(string(i))
+		m.Has(string(rune(i)))
 	}
 }